FindViewById (android.R.id.progress) returns null

Question

Android developers provide R.id.progress links among the built-in resources of available resources.

However, when I issue (in my activity class) a statement:

View pv = getWindow().findViewById(android.R.id.progress); 

It returns null.

It returns null even if I use it in conjunction with the ProgressBar class:

 ProgressBar pv = (ProgressBar) getWindow().findViewById(android.R.id.progress); 

And it returns null even without getWindow () :

 ProgressBar pv = (ProgressBar) findViewById(android.R.id.progress); 

Any idea why?

So that I would not hallucinate, I followed the advice of @Geobits and created a new project from scratch containing the exact code specified in the blog post recommended by @ArunGeorge below:

 package com.droidworks; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.widget.ProgressBar; public class ProgressBarExampleActivity extends Activity { private ProgressBar mProgress; private MyThread mBgThread; private final Handler mHandler = new Handler(); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mProgress = (ProgressBar) findViewById(android.R.id.progress); mBgThread = (MyThread) getLastNonConfigurationInstance(); if (mBgThread == null) { mBgThread = new MyThread(); mBgThread.start(); } mHandler.post(mThreadWatcher); } @Override public Object onRetainNonConfigurationInstance() { return mBgThread; } @Override protected void onPause() { mHandler.removeCallbacks(mThreadWatcher); super.onPause(); } private Runnable mThreadWatcher = new Runnable() { public void run() { int progress = mBgThread.getProgress(); mProgress.setProgress(progress); if (progress != 100) mHandler.postDelayed(this, 50); } }; static class MyThread extends Thread { private int _progress = 0; public void run() { for (; _progress < 100; _progress++) { try { Thread.sleep(100); } catch (InterruptedException ignored) { } } } private int getProgress() { return _progress; } } } 

Of course, this code raises a NullPointerException :

 at com.droidworks.ProgressBarExampleActivity$1.run(ProgressBarExampleActivity.java:44) at android.os.Handler.handleCallback(Handler.java:587) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:123) at android.app.ActivityThread.main(ActivityThread.java:4627) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:521) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) at dalvik.system.NativeStart.main(Native Method) 

Answer 1

The built-in R.id.progress tag is for the ProgressBar class. If you do not have a ProgressBar or ProgressBar object in your XML, it will return null.

Answer 2

EDITED

Sorry, I probably counted it wrong. this is what I get for not inserting. In any case, is there a reason why you are not just using one of the ProgressBar constructors? Here is a line from the last project I used the panel in:

 mProgress = new ProgressBar(this, null, android.R.attr.progressBarStyleHorizontal); 

Answer 3

android.R.id.progress used in conjunction with the ProgressBar .

Check out this link: http://foo.jasonhudgins.com/2010/03/simple-progressbar-tutorial.html

your use is thus incorrect.

Answer 4

From Eclipse, run the project clean by clicking Project> Clean ..., check the box next to your project and click OK. And try creating the project again.