I have two radio buttons and if one is selected I want to change the value of Textview. I am getting an error. The app stops working when I click one of my radio buttons. It is giving this error on log.
logged error
> /com.example.myapp.mttally E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.myapp.mttally, PID: 15125
java.lang.IllegalStateException: Could not execute method of the activity
at android.view.View$1.onClick(View.java:4025)
at android.view.View.performClick(View.java:4785)
at android.widget.CompoundButton.performClick(CompoundButton.java:120)
at android.view.View$PerformClick.run(View.java:19884)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5343)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4020)
at android.view.View.performClick(View.java:4785)
at android.widget.CompoundButton.performClick(CompoundButton.java:120)
at android.view.View$PerformClick.run(View.java:19884)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5343)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at
`com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
..`
My java code on main file is this
package com.example.myapp.mttally;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
RadioButton lend;
RadioButton borrow;
TextView toFrom;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView toFrom = (TextView) findViewById(R.id.toFrom);
RadioButton lend = (RadioButton) findViewById(R.id.lend);
RadioButton borrow = (RadioButton) findViewById(R.id.borrow);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
public void onRadioButtonClicked(View view) {
// Is the button now checked?
Boolean checked = ((RadioButton) view).isChecked();
// Check which radio button was clicked
switch (view.getId()) {
case R.id.lend:
if (checked)
toFrom.setText(" To");
break;
case R.id.borrow:
if (checked)
toFrom.setText(" From");
break;
}
}
}
Here my xml file
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context=".MainActivity">
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_marginTop="8dp"
android:id="#+id/linearLayout">
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:clickable="false"
>
<RadioGroup
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<RadioButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/radio_button1"
android:id="#+id/lend"
android:textSize="16dp"
android:onClick="onRadioButtonClicked"
/>
<RadioButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/radio_button2"
android:id="#+id/borrow"
android:textSize="16dp"
android:onClick="onRadioButtonClicked"
/>
</RadioGroup>
</LinearLayout>
</LinearLayout>
<TextView
android:layout_width="140dp"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:id="#+id/toFrom"
android:layout_below="#+id/linearLayout"
android:layout_centerHorizontal="true"
android:layout_marginTop="78dp" />
</RelativeLayout>
Every time you write something like TextView toFrom, RadioButton lend, or, more generally <type of variable> <variable name>, you're declaring a new variable. You declare variables called twoFrom, lend, and borrow in two places: once in the MainActivity class and once in the onCreate method. So, your code has two different variables that are both called toFrom, two variables called lend, and two variables called borrow.
Consider the lend variable. Each copy of the lend variable has its own "scope", or the area of code in which it exists. Since you declared the first lend variable in the class itself (not inside any of the methods), its scope is the class. You can (typically) use it in code anywhere in the class.
Your second lend variable, however, is what causes the problem. You've declared a second lend variable inside the onCreate method. That second lend is the one gets the TextView object...and then it ceases to exist once the onCreate method finishes executing.
So, to fix this, your onCreate should look like this:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toFrom = (TextView) findViewById(R.id.toFrom);
lend = (RadioButton) findViewById(R.id.lend);
borrow = (RadioButton) findViewById(R.id.borrow);
}
That way, when you get the reference to the TextView, you're holding it in the variable that will still exist when onRadioButtonClicked is called, not in a second identically-named variable that will cease to exist almost immediately.
Related
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I tried to add data to sqlite, but when I clicked Add Button error appear and my app closed. I don't understand, so many wasted hours for looking the solution by myself..
here is my java code, AddSampleActivity.java
package com.example.mangan;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class AddSampleActivity extends AppCompatActivity {
DatabaseHelper myDb;
EditText editNama, editJarak, editRating , editHarga;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_sample);
editNama = (EditText) findViewById(R.id.nama);
editJarak = (EditText) findViewById(R.id.jarak);
editRating = (EditText) findViewById(R.id.rating);
editHarga = (EditText) findViewById(R.id.harga);
myDb = new DatabaseHelper(this);
}
public void addData(View view) {
boolean isInserted = myDb.insertData(editNama.getText().toString(),
editJarak.getText().toString(),
editRating.getText().toString(),
editHarga.getText().toString() );
if(isInserted)
Toast.makeText(AddSampleActivity.this,"Data Inserted",Toast.LENGTH_LONG).show();
else
Toast.makeText(AddSampleActivity.this,"Data not Inserted",Toast.LENGTH_LONG).show();
}
}
my layout, activity_add_sample.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="10dp"
tools:context="com.example.mangan.AddSampleActivity">
<EditText
android:id="#+id/jarak_editText"
android:hint="Jarak"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<EditText
android:id="#+id/rating_editText"
android:hint="Rating"
android:layout_marginTop="10dp"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<EditText
android:id="#+id/harga_editText"
android:hint="Harga"
android:layout_marginTop="10dp"
android:layout_marginBottom="10dp"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<Button
android:id="#+id/add_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="addData"
android:text="Add"/>
</LinearLayout>
This is fullstack trace
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:5675)
at android.view.View$PerformClick.run(View.java:22651)
at android.os.Handler.handleCallback(Handler.java:836)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:208)
at android.app.ActivityThread.main(ActivityThread.java:6267)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5675)
at android.view.View$PerformClick.run(View.java:22651)
at android.os.Handler.handleCallback(Handler.java:836)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:208)
at android.app.ActivityThread.main(ActivityThread.java:6267)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
at com.example.mangan.AddSampleActivity.addData(AddSampleActivity.java:30)
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5675)
at android.view.View$PerformClick.run(View.java:22651)
at android.os.Handler.handleCallback(Handler.java:836)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:208)
at android.app.ActivityThread.main(ActivityThread.java:6267)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924)
It seem that some content on addData method is the problem. I read another question, Getting IllegalStateException on button click, but the problem is little bit different..
Your edittext ids aren't correct. change them like below
editJarak = (EditText) findViewById(R.id.jarak_editText);
editRating = (EditText) findViewById(R.id.rating_editText);
editHarga = (EditText) findViewById(R.id.harga_editText);
Your edit text ids are wrong. Try this,
editNama = (EditText) findViewById(R.id.nama_editText);
editJarak = (EditText) findViewById(R.id.jarak_editText);
editRating = (EditText) findViewById(R.id.rating_editText);
editHarga = (EditText) findViewById(R.id.harga_editText);
I have an issue with this botton, when is clicked the app send a message "ImageButton has stopped". I think it's something dumb, but I just started coding. Details of my code are below.
LogCat:
12-13 21:01:56.659 1075-1075/com.example.christian.imagebutton E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.christian.imagebutton, PID: 1075
java.lang.IllegalStateException: Could not find method llamar(MainActivity)(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatImageButton with id 'boton1'
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.resolveMethod(AppCompatViewInflater.java:327)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:284)
at android.view.View.performClick(View.java:5637)
at android.view.View$PerformClick.run(View.java:22429)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Main Activity
package com.example.christian.imagebutton;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private TextView tv1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv1=(TextView)findViewById(R.id.tv1);
}
public void llamar(View view){
tv1.setText("Llamando");
}
}
And the layout is:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.example.christian.imagebutton.MainActivity">
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:srcCompat="#mipmap/telefono"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:id="#+id/boton1"
android:onClick="llamar(MainActivity)" />
<TextView
android:text="TextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/boton1"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="22dp"
android:id="#+id/tv1" />
</RelativeLayout>
android:onClick="llamar"
Shouldn't it be like this?
Android just implements the OnClickListener for you when you define the android:onClick="someMethod" attribute.
Those two code snippets are totally the same but just implemented in two different ways.
Code Implementation
Button btn = (Button) findViewById(R.id.mybutton);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
llamar(v);
}
});
// some more code
public void llamar(View v) {
// does something very interesting
}
Above is a code implementation of an OnClickListener. And now the XML implementation.
XML Implementation
<?xml version="1.0" encoding="utf-8"?>
<!-- layout elements -->
<Button android:id="#+id/mybutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Click me!"
android:onClick="llamar" />
<!-- even more layout elements -->
Now in the background Android does nothing else than the Java code calling your method on a click event.
Note that with the XML above, Android will look for the onClick method llamar() only in the current Activity. This is important to remember if you are using fragments, since even if you add the XML above using a fragment, Android will not look for the onClick method in the .java file of the fragment used to add the XML.
This question already has answers here:
Your content must have a ListView whose id attribute is 'android.R.id.list'
(7 answers)
Closed 7 years ago.
here is the EditFriends activity..........................................
package com.josephvarkey996gmail.test1;
import android.app.ListActivity;
import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.Window;
import android.widget.ArrayAdapter;
import com.parse.FindCallback;
import com.parse.ParseException;
import com.parse.ParseQuery;
import com.parse.ParseUser;
import java.util.List;
public class Editfriends extends ListActivity {
public static final String Tag=Editfriends.class.getSimpleName();
protected List<ParseUser> mUser;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.activity_editfriends);
}
#Override
protected void onResume() {
super.onResume();
setProgressBarIndeterminateVisibility(true);
ParseQuery<ParseUser> query= ParseUser.getQuery();
query.orderByAscending(ParseConstants.key_Username);
query.setLimit(1000);
query.findInBackground(new FindCallback<ParseUser>() {
#Override
public void done(List<ParseUser> users, ParseException e) {
setProgressBarIndeterminateVisibility(true);
if (e== null){
mUser=users;
String[] username = new String[mUser.size()];
int i=0;
for(ParseUser user:mUser){
username[i]=user.getUsername();
i++;
}
ArrayAdapter<String> adapter = new ArrayAdapter<>(Editfriends.this,android.R.layout.simple_list_item_checked,username);
setListAdapter(adapter);
}
else
{
Log.e(Tag,e.getMessage());
AlertDialog.Builder builder=new AlertDialog.Builder(Editfriends.this);
builder.setMessage(e.getMessage()).setTitle(R.string.error_title).setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_editfriends, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
here is the xml of Editfriends ............................................
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context="com.josephvarkey996gmail.test1.Editfriends">
<TextView android:text="#string/hello_world" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
im learning ,so cant understand the eror. here is the logcat..............................
07-21 19:42:05.397 9188-9188/com.josephvarkey996gmail.test1 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.josephvarkey996gmail.test1, PID: 9188
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.josephvarkey996gmail.test1/com.josephvarkey996gmail.test1.Editfriends}: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list'
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list'
at android.app.ListActivity.onContentChanged(ListActivity.java:243)
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:382)
at android.app.Activity.setContentView(Activity.java:2145)
at com.josephvarkey996gmail.test1.Editfriends.onCreate(Editfriends.java:27)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Your main activity class is extending a ListActivity. This means that your xml file needs a ListView.
Try adding something like this to your XML:
<ListView android:id="#android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
More information can be found at http://developer.android.com/reference/android/app/ListActivity.html.
As the documentation states:
ListActivity has a default layout that consists of a single, full-screen list in the center of the screen. However, if you desire, you can customize the screen layout by setting your own view layout with setContentView() in onCreate(). To do this, your own view MUST contain a ListView object with the id "#android:id/list
Your activtiy extends ListActivity. So as the crash logs say :
Your content must have a ListView whose id attribute is 'android.R.id.list'
This mean that in your xml file you should have a ListView with the attribute android:id:"android.R.id.list.
This is because ListActivity expect to find a ListView in is content view.
You are using a ListActivity, which is a bit different than a normal Activity.
If you do nothing, then your ListActivity will have a single View in it, which is a ListView.
If you call setContentView() to supply your own layout (perhaps you want to display more than just a ListView), then your layout must contain a ListView and that ListView must have an id of #android:id/list.
Since you are providing a custom layout that consists of a RelativeLayout with a single TextView, your layout does not pass this requirement. Since it looks like you just have placeholder content there, I would remove the layout and remove the call to setContentView().
The exception you posted from your logcat mentions this:
Your content must have a ListView whose id attribute is 'android.R.id.list'
I'm new to Android developing. This is an assignment which was given to me. I have to convert the value and the converted value must be shown in the next activity. But when I press the submit button its crashes.I don;t know what is the problem. Is there a problem with my RadioButtons. Please help me...
This is the second activity(ConvertActivity)
package com.gihan.temperatureconverter;
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.RadioButton;
public class ConvertActivity extends ActionBarActivity {
//RadioButton cel=(RadioButton) findViewById(R.id.rCel);
//RadioButton fah=(RadioButton) findViewById(R.id.rFah);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_convert);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_convert, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public void calculation(View view) {
EditText val=(EditText) findViewById(R.id.editText);
int value = Integer.valueOf(val.getText().toString()).intValue();
int ans=0;
int fahval=0;
int celval=0;
boolean checked = ((RadioButton) view).isChecked();
switch(view.getId()) {
case R.id.rCel:
if (checked){
ans=((value-32)*5/9);
fahval=value;
celval=ans;}
break;
case R.id.rFah:
if (checked){
ans=((value*9)/5)+32;
celval=value;
fahval=ans;}
break;
}
/*if (cel.isChecked()){
ans=((value-32)*5/9);
fahval=value;
celval=ans;
}
if (fah.isChecked()){
ans=((value*9)/5)+32;
celval=value;
fahval=ans;
}*/
Intent intent = new Intent(ConvertActivity.this, LastActivity.class);
intent.putExtra("celval", getText(celval));
intent.putExtra("fahval", getText(fahval));
ConvertActivity.this.startActivity(intent);
}
}
This is the 2nd XML(activity_convert)
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context="com.gihan.temperatureconverter.ConvertActivity"
android:background="#drawable/ic_background">
<EditText
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="#+id/editText"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="50dp"
android:hint="Enter Value"
android:textSize="20dp"/>
<RadioGroup
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/radioGroup"
android:layout_below="#+id/editText"
android:layout_centerHorizontal="true">
<RadioButton
android:layout_width="200dp"
android:layout_height="wrap_content"
android:text="To Celsius"
android:id="#+id/rCel"
android:layout_below="#+id/editText"
android:layout_centerHorizontal="true"
android:layout_marginTop="50dp"
android:checked="false"
android:gravity="fill_horizontal"
android:textColor="#ffc80301"
android:textSize="25sp"/>
<RadioButton
android:layout_width="200dp"
android:layout_height="wrap_content"
android:text="To Fahrenheit"
android:id="#+id/rFah"
android:checked="false"
android:gravity="fill_horizontal"
android:textColor="#ffc80301"
android:textSize="25sp"
android:layout_below="#+id/rCel"
android:layout_alignLeft="#+id/rCel"
android:layout_alignStart="#+id/rCel" />
</RadioGroup>
<Button
android:layout_width="200dp"
android:layout_height="wrap_content"
android:text="Submit"
android:id="#+id/sub"
android:onClick="calculation"
android:layout_below="#+id/radioGroup"
android:layout_centerHorizontal="true"
android:layout_marginTop="80dp" />
</RelativeLayout>
This is the 3rd activity(LastActivity)
package com.gihan.temperatureconverter;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
public class LastActivity extends ActionBarActivity {
TextView vFah=(TextView)findViewById(R.id.vFah);
TextView vCel=(TextView)findViewById(R.id.vCel);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_last);//use whatever layout you want.
Bundle extras = getIntent().getExtras();
int celval=extras.getInt("celval");
int fahval=extras.getInt("fahval");
//String cel=String.valueOf(celval);
//String fah=String.valueOf(fahval);
vCel.setText(Integer.toString(celval));
vFah.setText(Integer.toString(fahval));
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_convert, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public void again(View view) {
Intent intent = new Intent(LastActivity.this, ConvertActivity.class);
LastActivity.this.startActivity(intent);
}
public void home(View view) {
Intent intent = new Intent(LastActivity.this, MainActivity.class);
LastActivity.this.startActivity(intent);
}
}
This is the 3rd XML(activity_last)
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/ic_background"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context="com.gihan.temperatureconverter.LastActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Successfully Converted"
android:id="#+id/textView2"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="30dp"
android:textColor="#ffff0004"
android:textSize="30sp"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Home"
android:id="#+id/button2"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="70dp"
android:gravity="center_horizontal"
android:textSize="25sp"
android:onClick="home"/>
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Calculate again"
android:id="#+id/button3"
android:layout_marginBottom="45dp"
android:gravity="center_horizontal"
android:layout_above="#+id/button2"
android:layout_centerHorizontal="true"
android:textSize="25sp"
android:onClick="again"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Fahrenheit"
android:id="#+id/textView3"
android:layout_below="#+id/textView2"
android:layout_centerHorizontal="true"
android:layout_marginTop="30dp"
android:textColor="#ff0010ff" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Celsius"
android:id="#+id/textView4"
android:layout_below="#+id/textView3"
android:layout_centerHorizontal="true"
android:layout_marginTop="52dp"
android:textColor="#ff0010ff" />
<TextView
android:layout_width="wrap_content"
android:layout_height="20sp"
android:id="#+id/vFah"
android:layout_below="#+id/textView3"
android:layout_centerHorizontal="true"
android:textColor="#ff9300ff"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="20sp"
android:id="#+id/vCel"
android:layout_below="#+id/textView4"
android:layout_centerHorizontal="true"
android:textColor="#ff9300ff"/>
</RelativeLayout>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.gihan.temperatureconverter" >
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".ConvertActivity"
android:label="#string/app_name">
</activity>
<activity
android:name=".LastActivity"
android:label="#string/app_name">
</activity>
</application>
</manifest>
Logcat
--------- beginning of crash
06-09 21:05:58.413 2381-2381/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.gihan.temperatureconverter, PID: 2381
java.lang.IllegalStateException: Could not execute method of the activity
at android.view.View$1.onClick(View.java:4020)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4015)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatButton cannot be cast to android.widget.RadioButton
at com.gihan.temperatureconverter.ConvertActivity.calculation(ConvertActivity.java:56)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4015)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Some Comments were some ways I tried. It's also failed.
And also this is Android Studio Project.
Your Error Solved Check this code
mainactivity.java
public class MainActivity extends ActionBarActivity {
EditText val;
public static int ans;
public static String fahval="";
public static String celval="";
RadioButton Box1,Box2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
val =(EditText) findViewById(R.id.editText);
}
public void calculation(View v)
{
//get value from edit text box and convert into double
double a=Double.parseDouble(String.valueOf(val.getText()));
Box1 = (RadioButton) findViewById(R.id.rCel);
Box2 = (RadioButton) findViewById(R.id.rFah);
//check which radio button is checked
if(Box1.isChecked())
{
//display conversion
celval = String.valueOf(f2c(a));
// Toast.makeText(getApplicationContext(), celval,Toast.LENGTH_LONG).show();
Box1.setChecked(true);
}
else
{
fahval = String.valueOf(c2f(a));
// Toast.makeText(getApplicationContext(), fahval,Toast.LENGTH_LONG).show();
Box2.setChecked(true);
}
Intent intent = new Intent(this, LastActivity.class);
intent.putExtra("celval", celval);
intent.putExtra("fahval", fahval);
startActivity(intent);
}
//Celcius to Fahrenhiet method
private double c2f(double c)
{
return (c*9)/5+32;
}
//Fahrenhiet to Celcius method
private double f2c(double f)
{
return (f-32)*5/9;
}
}
LastActivity.java
public class LastActivity extends ActionBarActivity {
TextView vFah;
TextView vCel;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.last);//use whatever layout you want.
vFah=(TextView)findViewById(R.id.vFah);
vCel=(TextView)findViewById(R.id.vCel);
Bundle extras = getIntent().getExtras();
String celval=extras.getString("celval");
String fahval=extras.getString("fahval");
//String cel=String.valueOf(celval);
//String fah=String.valueOf(fahval);
vCel.setText(celval);
vFah.setText(fahval);
}
public void again(View view) {
Intent intent = new Intent(LastActivity.this, MainActivity.class);
LastActivity.this.startActivity(intent);
}
public void home(View view) {
Intent intent = new Intent(LastActivity.this, MainActivity.class);
LastActivity.this.startActivity(intent);
}
}
I was building some apps this week, and couldn't figure out why I couldn't navigate from the Main Activity to a second activity and from there to a 3rd level activity (that would pop to 2nd activity), and app kept crashing when I added the 3rd. Finally looked in the Logcat to figure out what's wrong, and then read "Cannot Navigate from 'second activity'.... This View will not accept Navigation". Searched through code to find errors, but Never thought to look there before.
I’m working on a simple Quiz app where the user is presented a question and can select either True or False to answer the question. I added a “Show Answer” button, but when I click on that button I’m getting the following NullPointerException. I think I'm missing something in my activity_cheat.xml but I can't figure out what.
05-31 19:30:59.238 5978-5978/com.bignerdranch.android.geoquiz.geoquiz E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.bignerdranch.android.geoquiz.geoquiz, PID: 5978
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(int)' on a null object reference
at com.bignerdranch.android.geoquiz.geoquiz.CheatActivity$1.onClick(CheatActivity.java:33)
at android.view.View.performClick(View.java:5197)
at android.view.View$PerformClick.run(View.java:20926)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5942)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
CheatActivity.java
package com.bignerdranch.android.geoquiz.geoquiz;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class CheatActivity extends Activity {
private boolean mAnswerIsTrue;
private TextView mAnswerTextView;
private Button mShowAnswer;
public static final String EXTRA_ANSWER_IS_TRUE = "com.bignerdranch.android.geoquiz.answer_is_true";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_cheat);
mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, false);
mShowAnswer = (Button)findViewById(R.id.showAnswerButton);
mShowAnswer.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (mAnswerIsTrue) {
mAnswerTextView.setText(R.string.true_button);
} else {
mAnswerTextView.setText(R.string.false_button);
}
}
});
}
}
activity_cheat.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
android:gravity="center">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="24dp"
android:text="#string/warning_text_view" />
<TextView
android:id="#+id/answerTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="24dp" />
<Button
android:id="#+id/showAnswerButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/show_answer_button" />
</LinearLayout>
You forgot to bind mAnswerTextView with the UI:
Add
mAnswerTextView = (TextView)findViewById(R.id.answerTextView);
after the line
setContentView(R.layout.activity_cheat);
mAnswerTextView is never initialized. That's why you get the NPE.
add
mAnswerTextView = (TextView)findViewById(R.id.answerTextView);
before
if (mAnswerIsTrue)
mAnswerTextView is null.
Add,
mAnswerTextView = (TextView) findViewById(R.id.answerTextView);
before your onClickListener.