I am trying to change the text in one of the textview by calling it in a function that is assigned to a button.. However it is not quite working as I hoped. I was wondering if some one could point out why isn't it working?
Here is the "MainActivity.java" file
package com.nblsoft.myapplication;
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.TextView;
public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#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;
}
#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);
}
String stri = new String("Hellow");
public void game(View view) {
TextView textv = (TextView) findViewById(R.id.textView2);
textv.setText(stri);
}
}
and the "activity_main.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">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="#string/Welcome"
android:id="#+id/textView"
android:gravity="center"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:text="#string/lower_text"
android:id="#+id/textView2"
android:layout_below="#+id/editText"
android:layout_centerHorizontal="true"
android:layout_marginTop="34dp" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/editText"
android:inputType="number"
android:text="#string/guess"
android:textSize="160dp"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"
android:onClick="game"/>
<Button
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ok"
android:id="#+id/button"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
</RelativeLayout>
you want call game when click in EditText?! you put android:onClick="game" in EditText
if want call when click in Button you must add android:onClick="game" to your Button in activity_main.xml file like
<Button
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ok"
android:id="#+id/button"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:onClick="game" />
or you can use this in MainActivity.java instead use android:onClick="game" in xml file
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button=(Button) findViewById(R.id.button);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
game(arg0);
}
});
}
- remove android:onClick="game" from EditText
package com.nblsoft.myapplication;
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.TextView;
public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView textv = (TextView) findViewById(R.id.textView2);
String stri = new String("Hellow");
Button btn = (Button) findViewById(R.id.button);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
textv.setText(stri);
}
});
}
#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;
}
#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);
}
}
This should be working.By the way.Don't rush into android like this...you've got to learn a few things about how it works before you can play with it.Try to check the documentation and play with all that android offers.It's actually fun.It was for me and it still is as I've got to learn a lot ,still.
you call the method game() when you click the edittext "editText", and this will change the textview. If you want to change the value of the textview by clicking button "button", i think you just need to move the game() method to the Button field:
<Button
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ok"
android:id="#+id/button"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:onClick="game" />
Related
I'm getting a "cannot resolve symbol variable" on maleButton, on the bottom where the femaleSelected is. I've defined the RadioButtons in onCreate(). I thought onCreate() was protected, and that's why I couldn't access the buttons. But changing it into public solves nothing.
Here's the relevant code:
package ideaman924.playground;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.RadioButton;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RadioButton maleButton,femaleButton;
maleButton = (RadioButton) findViewById(R.id.male);
femaleButton = (RadioButton) findViewById(R.id.female);
}
#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;
}
#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 femaleSelected(View view) {
maleButton.toggle(); // error
}
}
Any idea why this is happening?
EDIT: Here is also the XML layout:
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="16dp"
android:orientation="vertical">
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:text="Select gender" />
<RadioButton
android:id="#+id/female"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:text="female"
android:onClick="femaleSelected" />
<RadioButton
android:id="#+id/male"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:text="male"
android:onClick="maleSelected" />
</LinearLayout>
Your RadioButton malebutton is a local variable and it is visible only in that method.
If you want to see it at the class level, you should move
RadioButton malebutton,femalebutton;
after
public class MainActivity extends AppCompatActivity {
Read about variables.
you need to define RadioButton malebutton out of onCreate method global variable for your class.
RadioButton malebutton,femalebutton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//RadioButton maleButton,femaleButton;
maleButton = (RadioButton) findViewById(R.id.male);
femaleButton = (RadioButton) findViewById(R.id.female);
}
I have tried searching for answers but i haven't found the fix for my problem yet. I have 2 activities -apple and Bacon. I am trying to learn intents and data passing between activities. The apple activity is supposed to pass the value entered in the EditText field on a button click to the bacon activity which just displays the value.
I am getting the following exception on the stack
Caused by: java.lang.NullPointerException: Attempt to invoke
virtual method 'android.text.Editable android.widget.EditText.getText()'
on a null object reference
The code snippets are as follows:-
apples.xml
<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=".Apple"
android:background="#009900">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Apples"
android:id="#+id/applesText"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Go to Bacon"
android:id="#+id/applesButton"
android:layout_below="#+id/applesText"
android:layout_centerHorizontal="true"
android:layout_marginTop="104dp"
android:onClick="onClickApples"/>
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="textPersonName"
android:ems="10"
android:id="#+id/personName"
android:layout_below="#+id/applesText"
android:layout_centerHorizontal="true" />
Apples.java
package com.example.karan.intentexample;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.content.Intent;
import android.widget.EditText;
public class Apple extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_apple);
}
#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_apple, 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 onClickApples(View view){
final EditText applesInput = (EditText)view.findViewById(R.id.personName);
String userMessage = applesInput.getText().toString();
Intent i = new Intent(this, Bacon.class);
//putExtra takes data in the form of a key-value pair
i.putExtra("appleMessage", userMessage);
startActivity(i);
}
}
Bacon.xml
<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.example.karan.intentexample.Bacon"
android:background="#72231F">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Bacon"
android:id="#+id/baconText"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="39dp" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New Button"
android:id="#+id/baconButton"
android:layout_below="#+id/baconText"
android:layout_centerHorizontal="true"
android:layout_marginTop="99dp" />
Bacon.java
package com.example.karan.intentexample;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
public class Bacon extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bacon);
Bundle applesData;
applesData = getIntent().getExtras();
//if there is no data in the intent
if(applesData==null)
return;
//get value by using the key in the getString method
String appleMessage = applesData.getString("appleMessage");
final TextView baconText = (TextView)findViewById(R.id.baconText);
baconText.setText(appleMessage);
}
#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_bacon, 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:
final EditText applesInput = (EditText)view.findViewById(R.id.personName);
view.findViewById causing issue.change it to:
final EditText applesInput = (EditText)Apple.this.findViewById(R.id.personName);
Because EditText with personName id is in Activity layout instead of inside Button layout(view parameter of onClickApples)
public class Apple extends AppCompatActivity {
private EditText applesInput;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_apple);
applesInput = (EditText)findViewByID(R.id.personName);
}
public void onClickApples(View view){
String userMessage = applesInput.getText().toString();
Intent i = new Intent(this, Bacon.class);
//putExtra takes data in the form of a key-value pair
i.putExtra("appleMessage", userMessage);
startActivity(i);
}
}
I want it so that when I click a button the text will become visible.
I failed.
Please, help me
Loveandriod.java
package com.example.farjad.andriodlove;
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.TextView;
public class LoveAndriod extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_love_andriod);
}
public void onLoveButtonClicked(View view){
TextView.setVisibility(R.id.haikowtext);
TextView haikotext=findViewById(View.VISIBLE);
}
#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_love_andriod, 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);
}
}
and the activity log is below;
activity.love_andriod.xml
<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=".LoveAndriod">
<TextView android:text="#string/hello_world"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/haikowtext"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="123dp"
android:visibility="invisible" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/love_button_text"
android:id="#+id/button"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:onClick="onLoveButtonClicked"/>
</RelativeLayout>
How can I sove that?
I am a beginner with Android Studio.
Try this:
TextView haikotext = (TextView)findViewById(R.id.haikowtext);
haikotext.setVisibility(View.VISIBLE);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_love_andriod);
TextView tv = (TextView)findViewById(R.id.haikowtext);
}
public void onLoveButtonClicked(View view){
tv.setVisibility(View.VISIBLE);
}
Hello I have an android application i want to create something like a lock button to the prevent error click on any button in application i use this method and it work great in disable all button i like but i can not re-enable it again after this all i need is that when i press lock button again it re-enable button2 and button 3 again
This is the activity code
import android.support.v7.app.ActionBarActivity;
import android.app.ActionBar;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.view.View;
public class AboutActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_about);
ActionBar actionBar = getActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
addListenerOnButton();
}
Button button;
Button button2;
Button button3;
private void addListenerOnButton() {
// TODO Auto-generated method stub
button = (Button) findViewById(R.id.lock);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
button2.setEnabled(false); //button which u want to disable
button3.setEnabled(false); //button which u want to disable
}
});
button2 = (Button) findViewById(R.id.button2);
button2.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
}
});
button3 = (Button) findViewById(R.id.button3);
button3.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.about, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
This is layout code
<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: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.lock.AboutActivity$PlaceholderFragment" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/hello_world" />
<Button
android:id="#+id/lock"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/textView1"
android:layout_centerHorizontal="true"
android:layout_marginTop="70dp"
android:text="Button" />
<Button
android:id="#+id/button3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="#+id/button2"
android:layout_below="#+id/button2"
android:layout_marginTop="66dp"
android:enabled="true"
android:text="Button" />
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/lock"
android:layout_centerVertical="true"
android:enabled="true"
android:text="Button" />
</RelativeLayout>
You can use isEnabled() and use "not" operator to lock and unlock. If it's not enabled, it'll enable and vice versa.
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
button2.setEnabled(!button2.isEnabled()); //button which u want to disable
button3.setEnabled(!button3.isEnabled()); //button which u want to disable
}
});
Something very weird is happening in my program. I try to use the button with the first program below (using an emulator) and the program did not even open. So I changed to the second version, using the android:OnClick, and it did not work either (the program opened, but in the click it crashed). Then I tried the third program, using android:onCLick and the instanciation of the EditText in the treatment function, and the program worked.
Can someone explain to me why the first two programs did not worked?
Edit: I noticed now that LogCat is pointing to the following error: error opening trace file: No such file oor directory (2), what is that? Can it have any relation to this error?
And if I comment the definition of the onClickListener to b1 the program do not crash anymore.
First code:
package app.projetnf33;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
public class MainActivity extends Activity implements OnClickListener{
String[] names;
EditText status;
EditText par1;
EditText par2;
EditText par3;
Button b1;
Button b2;
Button b3;
Button b4;
Spinner spin;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
status = (EditText) findViewById(R.id.text);
b1 = (Button) findViewById(R.id.b1);
b1.setOnClickListener(new OnClickListener(){
#Override
public void onClick(View v) {
status.setText("Connect");
}
});
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
}
}
Second code
package app.projetnf33;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
public class MainActivity extends Activity implements OnClickListener{
String[] names;
EditText status;
EditText par1;
EditText par2;
EditText par3;
Button b1;
Button b2;
Button b3;
Button b4;
Spinner spin;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
status = (EditText) findViewById(R.id.text);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
public void treatment_connect(View v){
status.setText("Connect");
}
public void treatment_persons(View v){
status.setText("Persons");
}
public void treatment_lecture(View v){
status.setText("Lecture");
}
public void treatment_execute(View v){
status.setText("Execute");
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
}
}
Third code (which worked):
package app.projetnf33;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
public class MainActivity extends Activity implements OnClickListener{
String[] names;
EditText status;
EditText par1;
EditText par2;
EditText par3;
Button b1;
Button b2;
Button b3;
Button b4;
Spinner spin;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
public void treatment_connect(View v){
status = (EditText) findViewById(R.id.text);
status.setText("Connect");
}
public void treatment_persons(View v){
status.setText("Persons");
}
public void treatment_lecture(View v){
status.setText("Lecture");
}
public void treatment_execute(View v){
status.setText("Execute");
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
}
}
Fragment_layout:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/tex_status" />
<EditText
android:id="#+id/text"
android:inputType="text"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
<Spinner
android:id="#+id/spinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/par1" />
<EditText
android:id="#+id/par1"
android:inputType="text"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/par2" />
<EditText
android:id="#+id/par2"
android:inputType="text"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/par3" />
<EditText
android:id="#+id/par3"
android:inputType="text"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="#+id/b1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:drawableLeft="#drawable/ic_action_usb"
android:gravity="center_vertical"
android:text="#string/connect"
android:onClick="treatment_connect" />
<Button
android:id="#+id/b2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:drawableLeft="#drawable/ic_action_computer"
android:gravity="center_vertical"
android:text="#string/read"
android:onClick="treatment_lecture" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="#+id/b3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:drawableLeft="#drawable/ic_action_accept"
android:gravity="center_vertical"
android:text="#string/execution"
android:onClick="treatment_execution" />
<Button
android:id="#+id/b4"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:drawableLeft="#drawable/ic_action_warning"
android:gravity="center_vertical"
android:text="#string/disconnect"
android:onClick="treatment_disconnect" />
</LinearLayout>
</LinearLayout>
In the first and seconds layout you tried to call
status = (EditText) findViewById(R.id.text);
b1 = (Button) findViewById(R.id.b1);
before
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
So you tried to reference a Button and EditText contained in the PlaceholderFragment layout before you created the fragment.
The views are in the fragment layout. It only becomes a part of the activity view hierarchy after the fragment transaction has been run. Your pending fragment transaction is executed in activity super.onStart() which comes only after onCreate(). In essence, you're calling findViewById() too early in the first two versions. The third version works because the findViewById() is in the click handler and gets invoked when the fragment is attached to the activity.
Usually you'd call findViewById() to set up listeners and so on at the earliest possibility in fragment onCreateView(), just after the fragment layout is inflated.