I am trying to make an simple button that will cooperate with TextView, array and method changer (in public class Change). However the application uses the method changer only twice (below). It should work on every click. The changer method is used for the change in displayed array.
1-click: 1 |
2-click: 4 |
3-click: 1 |
4-click: 1 |
...-click: 1 |
I don't know where is the problem.
My target solution should be 1,4,1,4,1,4 ...
MainActivity.java
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
String[] numbers = {"1", "2","3","4"};
private Button mButton;
int i = 0;
Change ch = new Change();
TextView text;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mButton = (Button) findViewById(R.id.button2);
text = (TextView) findViewById(R.id.tv1);
ch = new Change();
mButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
text.setText(numbers[0]);
numbers = ch.changer(numbers);
i++;
}
});
}
}
Change.java
public class Change {
String[] arraynew = new String[4];
public String[] changer(String[] array){
arraynew[0]=array[3];
arraynew[1]=array[2];
arraynew[2]=array[1];
arraynew[3]=array[0];
return arraynew;
}
}
The arraynew variable in your code is global - so it will not create a new array every time you call the changer method, only rearranges its contents.
Here comes the tricky part: When you call the method for the second time, the parameter is the same object as arraynew. So when you do arraynew[0]=array[3] it changes 4 to 1 on the first slot; but arraynew[3]=array[0] will copy that newly changed 1 to the third index (where it is still the same 1 you put there). It basically eliminates the 4, making it impossible to recover.
Solution: Make arraynew local. If you declare it in the method, it will never be the same array, so the issue won't appear.
Related
I am new to Android programming and tried to create a small App. I have a MainClass with one EditText and one TextField. EditText is for users to type in a number and the TextField shows the value of the input when clicking on the first button. The second button is for switching to the other class (MainClass2). Now i want to show the input number from EditText (that I defined as "number") in the next class MainClass2 in an empty TextField. I implemented an OnClickListener for the two different buttons mentioned in the MainClass (first screen). Since I only defined the input variable "number" when clicking the first button (cause "number" is then shown in the TextField as mentioned because it is only created via EditText when clicking the first button), "number" is not defined in the code of clicking the second button. Therefore I cant hand it over to the MainClass2 via Intent. Do you have any solutions for this? Thank you in advance. These are the codes for my Classes:
package com.example.teilnehmeranzahl;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.util.Random;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = findViewById(R.id.button);
Button button2 = findViewById(R.id.button2);
Button one = (Button) findViewById(R.id.button);
one.setOnClickListener(this); // calling onClick() method
Button two = (Button) findViewById(R.id.button2);
two.setOnClickListener(this);
}
public void onClick(View v) {
// default method for handling onClick Events..
switch (v.getId()) {
case R.id.button:
EditText editText2 = findViewById(R.id.editText2);
String name2=editText2.getText().toString();
int number=Integer.parseInt(name2);
TextView textView = findViewById(R.id.textView);
textView.setText(String.valueOf(number));
Random randomizer = new Random();
int name = randomizer.nextInt(number+1);
TextView textView2 = findViewById(R.id.textView2);
if (name == 1 ) {
textView2.setText("Player 1");
}
if (name == 2 ) {
textView2.setText("Player 2");
}
break;
case R.id.button2:
Intent intent = new Intent(MainActivity.this,MainActivity2.class);
intent.putExtra("number",number); //here is the error cause number is not
defined, although it is..
startActivity(intent);
break;
default:
break;
}
}
}
And this is the code for MainClass2:
package com.example.teilnehmeranzahl;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
public class MainActivity2 extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
TextView textView3 = findViewById(R.id.textView3);
Intent intent = getIntent();
String number = intent.getStringExtra("number");
textView3.setText(number);
}
}
In case R.id.button2: you have not set the value of number. So it will give number undefined error. To solve this issue either you have to initialize number globally or get the value of number in case R.id.button2: also. Like
case R.id.button2:
EditText editText2 = findViewById(R.id.editText2);
String name2=editText2.getText().toString();
int number=Integer.parseInt(name2);
Intent intent =
new Intent(MainActivity.this,MainActivity2.class);
intent.putExtra("number",number);
startActivity(intent);
break;
First I must say that I'm not good in English and "completely new" to Android Programming.
I want to create an app that can monitor server performance. I have use the navigation drawer as my app interface. Each have a few fragment running with different sets of activity. One of the fragment, I would like to create an activity that can calculate the server performance using some if else statement calculation with a button to submit the results. When I run my app, I have trouble with this fragment (FuzFragment) where my app stopped immediately with an error "Unfortunately, ServerMonitorApp has stopped".
Below, is the fragment class (FuzFragment) that I used to display the layout:
package com.example.servermonitorapp;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;
public class FuzFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (container == null) {
return null;
}
LinearLayout mLinearLayout = (LinearLayout) inflater.inflate(R.layout.fragment_fuz,
container, false);
Button sumButton = (Button) mLinearLayout.findViewById(R.id.submitButton);
sumButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
EditText cpu = (EditText) v.findViewById(R.id.textCPU);
EditText ram = (EditText) v.findViewById(R.id.textRAM);
TextView res = (TextView) v.findViewById(R.id.txtResult);
int cpuslow = Integer.parseInt(cpu.getText().toString());
int cpusmedium = Integer.parseInt(cpu.getText().toString());
int cpushigh = Integer.parseInt(cpu.getText().toString());
int ramlow = Integer.parseInt(ram.getText().toString());
int rammedium = Integer.parseInt(ram.getText().toString());
int ramhigh = Integer.parseInt(ram.getText().toString());
if (cpuslow > 0 && cpuslow <= 30 | ramlow > 0 && ramlow <= 23) {
res.setText("Safe");
} else if (cpusmedium > 30 && cpusmedium <= 60 | rammedium > 23 && rammedium <= 38) {
res.setText("Risk");
} else if (cpushigh > 60 | ramhigh > 38) {
res.setText("Very Risk");
} else {
res.setText("Invalid Number");
}
}
});
return mLinearLayout;
}
}
Is there any wrong with my code that can cause my app stopped responding? Need help so much on this since I'm still in learning in Android programming.
Welcome to Android the dark side of development haha ;).
Ok let's go through a few basics.
The onCreate method is used to inflate or draw your layout. prior to having your layout drawn (if you do a findViewById) it won't exist.
In order for the onCreate method to draw the picture it needs the setContent method called that is created by default. This should be one of if not the first line of code you call. It ensures everything is available after that line for UI related interactions of an ACTIVITY. Emphasis on activity because the rules change when you get into fragments.
Now, the next issue is you have bloated code. Doing things like.
EditText myText = findViewById(R.id.myText);
int myValue = Integer.parseInt(myText.getText.toString());
etc.. can all be done in the same line and you are not using the reference to myText anywhere else so just do it like:
int myValue = Integer.parseInt(findViewById(R.id.myText).getText.toString());
Keep in mind I am doing Pseudo code. Please don't be that person that replies with " you have an error in your code " haha or I will not help.
Next up, it appears you never did the setContentView method in your onCreate, please put that back and set the content to your activity.xml code that matches the layout that you are inflating.
Next up, you are doing findViewById inside a button click. This is unnecessary repeat code. If you need to use the textView over and over then store a reference to it to avoid the repetitive lookup.
class MyClass{
EditText myTextBox;
protected void onCreate(stuff){
myTextBox = findViewById(R,id.myTextBox);
findViewById(R.id.myButton).setOnClickListener(new OnClickListener()){
#Override
protected void onClick(){
int myValue = Integer.parseInt(myTextBox.getText().toString());
}
});
}
Also for the record the onCreate should be very clean and to the point. I typically have a syncUI method that does my findViewById calls "prior to data binding days". I don't do that anymore, but new guys learning is fine.
Then in my syncUI I call wrapper methods to handle click listening instead of nesting in onCreate, but for now you are learning. But if you want a quick example..
onCreate(){
setContentView(myViewPointer from the R File);
syncUI();
}
private void syncUI(){
//SETUP TEXTVIEWS OR OTHER UIs that you need
//get btnSubmit reference from findViewByid
btnSubmit_onClick(); //called one time in onCreate to wrap the click listener into method that allows it to collapse and be easily found.
}
private btnSubmit_onClick(){
btnSubmit.setOnClickListener(new OnClickListener(){
#Override
protected void onClick(){
//handle Clicks
}
});
}
Thanks Sam for your reply..
I hv figure out one of my issue that cause my fragment stop responding when I run my app is might due to I mistaken declare my layout as LinearLayout in code above where else my actual layout in the myfragment.xml file is in Relativelayout (shown below).
LinearLayout mLinearLayout = (LinearLayout) inflater.inflate(R.layout.fragment_fuz,
container, false);
After I correct it my app can be open and the fragment related above also able to open. Only there's still problem when I try to run the code using few number sample and my app stop responding with same error "Unfortunately, ServerMonitorApp has stopped".
I'm a noob Android studio programmer (this is hour 2 of learning!) and I expect this is a real rookie error I'm making!
I've got a Plain Text field in my application and I would like to set the text of this dynamically. I've given the plain text field the ID of: "resultText". Here's what I try;
public void calcnums(View v)
{
int x=firstNum + seondNum;
resultText.setText("Result: " + x);
}
For some reason I get 'resultText' highlighted in red and the hover over message is; Cannot resolve symbol 'resultText'.
I have the feeling that I'm doing something wrong by using the ID, but I'm lost!
Full code as suggested in comments;
import android.app.Application;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import java.util.Random;
public class AddNumbers extends AppCompatActivity {
private int firstNum;
private int seondNum;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_numbers);
}
public void calcnums(View v)
{
int x=firstNum + seondNum;
resultText.setText(String.format("Result: %d", x);
}
public void setNums(View v)
{
TextView tx= (TextView) findViewById(R.id.text);
Random r = new Random();
int x=r.nextInt(2) + 1; // r.nextInt(2) returns either 0 or 1
firstNum = x;
r = new Random();
x=r.nextInt(2) + 1;
seondNum = x;
num1.setText(""+firstNum);
num2.setText(""+seondNum);
}
}
It seems you need to declare the View resultText
Like,
EditText resultText = (EditText) findViewById(R.id.resultText);
Also make sure that the name you are using for the resultText View in xml is written correctly as provided in the method findViewById()
usually cannot resolve symbol means some problems in variable declarations.
I am too learning android and I stumbled upon this problem as well.
I don't have the whole snippet of your code.But the thing you might be missing is to point your EditText object to view in xml.
EditText resultText = (EditText) v.findViewById(R.id.result_edit_text);
<EditText
android:id="#+id/result_edit_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="#string/result_edit_text"
/>
Let's assume that we have an layout with an edittext
<EditText
android:id="#id/txt_user_email"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:inputType="text" />
It has an ID. In your actitivy you must find and cast the EditText as follow:
EditText txtUserEmail = (EditText) findViewById(R.id.txt_user_email);
txtUserEmail.setText("klaus.dieter#lusty-swingers.de");
You need to find your text view in onCreate(), like that:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_numbers);
TextView tx= (TextView) findViewById(R.id.text);
}
I know that title is fancy but this is going on in my android app.
I am storing the names of websites which user wants to open in an arraylist of strings. Then an array of buttons is made whose size depends on the size of arraylist.
Then I set the text of the buttons using the arraylist. This works perfectly and all the buttons are assigned correct text.
Then I set the on click listeners of each button and create an implicit intent to open the web site.
Problem that is occuring is that despite the fact the text of the buttons are set perfectly , There is some problem with the listener because no matter which button i press, always the site of last button is opened and hence last button dictatorship.
Here is my code.
package com.example.hp.myproject;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;
import java.util.ArrayList;
/**
* Created #CreativeLabsworks
*/
public class Act3 extends Activity
{
LinearLayout ll1; Button[] bt_arr; String s;
LinearLayout.LayoutParams params1;
ArrayList<String> sites;TextView t1;
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
Intent intent=getIntent();
sites= intent.getStringArrayListExtra("arraylist");
/*Creating a linear layout to hold editTexts*/
ll1=new LinearLayout(this);
ll1.setOrientation(LinearLayout.VERTICAL);
/*set the width and height of the linear layout*/
params1=new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);
setContentView(ll1, params1);
/*Initializing the button array*/
bt_arr = new Button[sites.size()];
/*Initialize each button*/
for(int i=0;i<bt_arr.length;++i)
{
bt_arr[i] = new Button(this);
ll1.addView(bt_arr[i]);
}
setText();
attach_listeners();
}
public void attach_listeners()
{
/*this function attaches listeners with all buttons in the button array*/
for(int i=0;i<bt_arr.length;++i)
{
s=sites.get(i);
bt_arr[i].setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
Intent i=new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse("http://"+s));
startActivity(i);
}
});
}
}
public void setText()
{
/*This function sets the text of the various buttons*/
int j;
for(int i=0;i<bt_arr.length;++i)
{
j=sites.get(i).indexOf(".com");
bt_arr[i].setText(sites.get(i).substring(4,j));
}
}
}
The problem that you have is that
s=sites.get(i);
S is being set by the last element.
Whenever a button is clicked it is taking the S from the last element since S is outside the onClickListener instance that you have.
I would suggest to save the url in the Button tag and then use it When the button is clicked.
for (int i = 0; i < bt_arr.length; ++i) {
s = sites.get(i);
bt_arr[i].setTag(s);
bt_arr[i].setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String website = (String)v.getTag();
Intent i = new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse("http://" + website));
startActivity(i);
}
});
}
Intent i=new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse("http://"+s));
startActivity(i);
Maybe you do not write i.setclass()?
I used to have some experience with developing for android but I started up again after 6 months and forgot most of it. I am now using a macbook to do my developing on and had to set up Eclipse, the Android SDK and AVD all over again and I'm worried I messed something up.
When I start a new project with the default activity that displays "Hello World" on my screen the app runs fine. I then tried to put in two buttons that cause the text in a new TextView to change. But whenever I include the textView part I get a runtime error. When I comment it out, the app runs but obviously nothing happens. Based upon the tutorials I've been reading, this is the appropriate place and way to declare/create the textView but I can't figure out what's wrong. Any suggestions?
[Edit] I was messing around and found that I can make the mytext a field instead of a TextView and that worked. So in my onCreate(), I put
mytext = (TextField)findViewById(R.id.TextView1);
but that doesn't seem the right way to do things.
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class IntroActivity extends Activity {
TextView myText = (TextView)findViewById(R.id.textView1);
//i've tried this with final added on to it as well (recommended by eclipse)
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setButtonClickListener();
}
private void setButtonClickListener() {
Button button1 = (Button)findViewById(R.id.button1);
Button button2 = (Button)findViewById(R.id.button2);
button1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
myText.setText("Hello");
}
});
button2.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// myText.setText("Goodbye");
}
});
}
}
This:
TextView myText = (TextView)findViewById(R.id.textView1);
should be separated. The declaration should be at the same place:
private TextView myText;
But the assignment should come only after setContentView:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
myText = (TextView)findViewById(R.id.textView1);
This is done since before setContentView, Dalvik doesn't know from which layout to take the view that matchs the id R.id.textView1