Android Task Tracker Async onProgressUpdate
I am a new programmer. I've seen a lot of tutorials but can't figure out what is wrong. I am trying to create a ProgressBar from an Async task. However, it always crashes my application.
Here's the main application:
package pt.flag.ensemble;
import java.util.Random;
import pt.flag.ensemble.task.AsyncTaskBar;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ProgressBar;
import android.widget.Toast;
public class Intervals extends Activity {
private static Intervals instance;
private Context context;
private String answer;
int right_question;
int wrong_question;
int randomInt2;
public ProgressBar progressBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_intervals);
// initializing the sounds
final MediaPlayer sound1 = MediaPlayer.create(Intervals.this,
R.raw.maj2);
final MediaPlayer sound2 = MediaPlayer.create(Intervals.this,
R.raw.maj3);
final MediaPlayer sound3 = MediaPlayer.create(Intervals.this,
R.raw.maj4);
//ProgressBar
instance=this;
ProgressBar progressBar = (ProgressBar) findViewById(R.id.Progressbar);
progressBar.setProgress(0);
// Play Methods
final ImageButton Play = (ImageButton) findViewById(R.id.Play);
Play.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
new AsyncTaskBar().execute();
Play.setEnabled(false);
// generate random number
Random randomGenerator = new Random();
int randomInt = randomGenerator.nextInt(3) + 1;
randomInt2 = randomInt;
// picking the right sound to play
switch (randomInt) {
case 1:
sound1.start();
answer = "M2";
break;
case 2:
sound2.start();
answer = "M3";
break;
case 3:
sound3.start();
answer = "P4";
break;
}
}
});
//Audio Repeat Methods
Button Repeat = (Button) findViewById(R.id.Repeat);
Repeat.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// picking the right sound to play
switch (randomInt2) {
case 1:
sound1.start();
new AsyncTaskBar().execute();
answer = "M2";
break;
case 2:
sound2.start();
new AsyncTaskBar().execute();
answer = "M3";
break;
case 3:
sound3.start();
new AsyncTaskBar().execute();
answer = "P4";
break;
}
}
});
}
//Answering Methods
public void buttonClicked2(View view) {
Button clickedButton = (Button) view;
if (clickedButton.getText().toString().equals(answer)) {
Toast.makeText(Intervals.this, "You are Right!", Toast.LENGTH_LONG)
.show();
right_question = right_question + 1;
final ImageButton Play = (ImageButton) findViewById(R.id.Play);
Play.setEnabled(true);
// Passing results through
SharedPreferences sharedPref = getSharedPreferences(
"INTERVALRIGHTS", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putInt("SCORE", right_question);
editor.commit();
} else {
Toast.makeText(Intervals.this, "You are Wrong!", Toast.LENGTH_LONG)
.show();
wrong_question = wrong_question + 1;
// Passing results through
SharedPreferences sharedPref02 = getSharedPreferences(
"INTERVALWRONGS", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref02.edit();
editor.putInt("SCORE02", wrong_question);
editor.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.intervals, 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.
switch (item.getItemId()) {
case R.id.action_settings:
Intent intent = new Intent(Intervals.this, IntervalResults.class);
startActivity(intent);
break;
default:
return super.onOptionsItemSelected(item);
}
return true;
}
public static Intervals getApp() { return instance; }
}
Here is the AsyncTask class
package pt.flag.eventapp.task;
import pt.flag.eventapp.Main;
import android.os.AsyncTask;
import android.os.SystemClock;
import android.widget.Toast;
public class ShowDialogAsyncTask extends AsyncTask<Void, Integer, Void> {
int progress_status;
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
//Toast.makeText(Main.getApp(),"Invoke on PreExecute()", Toast.LENGTH_SHORT).show();
progress_status = 0 ;
//Main.getApp().txt_percentage.setText("downloading 0%");
}
@Override
protected Void doInBackground(Void... params) {
while (progress_status < 100){
progress_status +=2;
publishProgress(progress_status);
SystemClock.sleep(300);
}
return null;
}
@Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
//Main.getApp().progressBar.setProgress(values[0]);
//Main.getApp().txt_percentage.setText("downloading" + values[0] + "%");
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
//Toast.makeText(Main.getApp(), "Invoke onPostExecute()", Toast.LENGTH_SHORT).show();
//Main.getApp().txt_percentage.setText("download complete");
}
}
Here is the log:
08-10 20:38:11.081: E/AndroidRuntime(21441): FATAL EXCEPTION: main
08-10 20:38:11.081: E/AndroidRuntime(21441): java.lang.NullPointerException
08-10 20:38:11.081: E/AndroidRuntime(21441): at pt.flag.ensemble.task.AsyncTaskBar.onProgressUpdate(AsyncTaskBar.java:34)
08-10 20:38:11.081: E/AndroidRuntime(21441): at pt.flag.ensemble.task.AsyncTaskBar.onProgressUpdate(AsyncTaskBar.java:1)
08-10 20:38:11.081: E/AndroidRuntime(21441): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:618)
08-10 20:38:11.081: E/AndroidRuntime(21441): at android.os.Handler.dispatchMessage(Handler.java:99)
08-10 20:38:11.081: E/AndroidRuntime(21441): at android.os.Looper.loop(Looper.java:156)
08-10 20:38:11.081: E/AndroidRuntime(21441): at android.app.ActivityThread.main(ActivityThread.java:4977)
08-10 20:38:11.081: E/AndroidRuntime(21441): at java.lang.reflect.Method.invokeNative(Native Method)
08-10 20:38:11.081: E/AndroidRuntime(21441): at java.lang.reflect.Method.invoke(Method.java:511)
08-10 20:38:11.081: E/AndroidRuntime(21441): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
08-10 20:38:11.081: E/AndroidRuntime(21441): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
08-10 20:38:11.081: E/AndroidRuntime(21441): at dalvik.system.NativeStart.main(Native Method)
If I'm correct, the log seems to indicate an error on line 34 in the AsyncTask class, which is "Intervals.getApp (). ProgressBar.setProgress (values [0]); I just don't know why ...
Also, here is my xml file
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<ImageButton
android:id="@+id/Play"
android:contentDescription="@string/hello_world"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_launcher"
android:layout_marginTop="50dp"
android:layout_marginLeft="50dp" />
<Button
android:id="@+id/Repeat"
android:contentDescription="@string/hello_world"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Repeat"
android:layout_marginTop ="50dp"
android:layout_toRightOf="@+id/Play"
android:layout_marginLeft="25dp" />
<ProgressBar
android:id="@+id/Progressbar"
style="@android:style/Widget.ProgressBar.Horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="test"
android:layout_marginTop="20dp"
android:layout_below="@+id/Play" />
<Button
android:id="@+id/Octave_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_marginLeft="5dp"
android:layout_below="@+id/Progressbar"
android:onClick="buttonClicked2"
android:layout_marginTop="100dp"
android:text="@string/octave" />
<Button
android:id="@+id/min2_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/Progressbar"
android:onClick="buttonClicked2"
android:layout_marginTop="100dp"
android:layout_toRightOf="@+id/Octave_Button"
android:text="@string/minor2" />
<Button
android:id="@+id/Maj2_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/Progressbar"
android:onClick="buttonClicked2"
android:layout_marginTop="100dp"
android:layout_toRightOf="@+id/min2_Button"
android:text="@string/major2" />
<Button
android:id="@+id/min3_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/Progressbar"
android:onClick="buttonClicked2"
android:layout_marginTop="100dp"
android:layout_toRightOf="@+id/Maj2_Button"
android:text="@string/minor3" />
<Button
android:id="@+id/Maj3_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/Progressbar"
android:onClick="buttonClicked2"
android:layout_marginTop="100dp"
android:layout_toRightOf="@+id/min3_Button"
android:text="@string/major3" />
<Button
android:id="@+id/P4_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/Progressbar"
android:onClick="buttonClicked2"
android:layout_marginTop="100dp"
android:layout_toRightOf="@+id/Maj3_Button"
android:text="@string/perfect4" />
<Button
android:id="@+id/A4_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/Octave_Button"
android:onClick="buttonClicked2"
android:layout_marginTop="15dp"
android:layout_marginLeft="5dp"
android:text="@string/tritone" />
<Button
android:id="@+id/P5_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/min2_Button"
android:onClick="buttonClicked2"
android:layout_marginTop="15dp"
android:layout_toRightOf="@+id/A4_Button"
android:text="@string/perfect5" />
<Button
android:id="@+id/minor6_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/Maj2_Button"
android:onClick="buttonClicked2"
android:layout_marginTop="15dp"
android:layout_toRightOf="@+id/P5_Button"
android:text="@string/minor6" />
<Button
android:id="@+id/Major6_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/min3_Button"
android:onClick="buttonClicked2"
android:layout_marginTop="15dp"
android:layout_toRightOf="@+id/minor6_Button"
android:text="@string/major6" />
<Button
android:id="@+id/minor7_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/Maj3_Button"
android:onClick="buttonClicked2"
android:layout_marginTop="15dp"
android:layout_toRightOf="@+id/Major6_Button"
android:text="@string/minor7" />
<Button
android:id="@+id/Major7_Button"
android:layout_width="52dp"
android:layout_height="80dp"
android:layout_below="@+id/P4_Button"
android:onClick="buttonClicked2"
android:layout_marginTop="15dp"
android:layout_toRightOf="@+id/minor7_Button"
android:text="@string/major7" />
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3 answers
I think it's better if you pass the progress bar as an argument to AsyncTask
:
final ProgressBar progressBar = (ProgressBar) findViewById(R.id.Progressbar);
progressBar.setProgress(0);
// Play Methods
final ImageButton Play = (ImageButton) findViewById(R.id.Play);
Play.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
AsyncTaskBar task = new AsyncTaskBar();
task.setProgressBar(progressBar);
task.execute();
}
And then AsyncTask
declare the method setProgressBar
:
public class ShowDialogAsyncTask extends AsyncTask<Void, Integer, Void> {
ProgressBar bar;
public void setProgressBar(ProgressBar bar) {
this.bar = bar;
}
@Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
if (this.bar != null) {
bar.setProgress(values[0]);
}
}
You can do the same with the TextView
one you are trying to install.
Anyway, since you mentioned that you are new to this, you might want to take a look at the Broadcast / Receiver template. Here's how it's done:
- Run the async task without setting a progress bar or whatever.
- Define
BroadcastReceiver
, instantiate in your activity and register / unregister. - Whenever there is a progress update in your asynchronous task, just call sendBroadcast with the progress update as an additional intent. You may need to pass a context parameter when instantiating AsyncTask.
- Your application's onHandleIntent method (the one you created in step 2) will run on the UI thread, making all these UI updates safe.
Sounds a little overwhelming? That's at first, but here are the benefits:
- It's much cleaner than passing UI objects to AsyncTask.
- You will learn a powerful Android pattern that comes in handy in other endeavors.
- This will save you a lot of hassle (and exceptions) if you switch context or your application gets low in memory.
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Intervals.getApp().progressBar.setProgress(values[0]);
This line of code has two possibilities for NullPointerException
:
-
getApp()
returnsnull
-
progressBar
null
To determine what the reason is, you need to break it down into two separate lines:
Intervals intervals = Intervales.getApp();
intervals.progressBar.setProgress(values[0]);
Now set a breakpoint on the first line, go to it and determine if there is intervals
null
or not.
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