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POWhy complains my code has not called Looper.prepare()
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copied!<p>I created a <strong>Looper thread</strong> class:</p> <pre><code>public class MyLooperThread extends Thread{ private Handler mHandler; public void init(){ start(); //start the thread synchronized (this) { wait(5000); //wait for run() } Log.d("DEBUG","Init Done!"); //EXCEPTION: Can't create handler inside thread that has not called Looper.prepare() MyObject obj = new MyObject(mHandler); } @Override public void run() { Looper.prepare(); mHandler = new Handler(){ @Override public void handleMessage(Message msg){ //Check installed app package names, NOTHING RELATED WITH UI ... } }; synchronized (this) { notify(); } Looper.loop(); }//end of run() } </code></pre> <p>In my <strong>Activity</strong>, I call above <code>MyLooperThread</code> 's <code>init()</code> method in <code>onCreate()</code>. Besides, I have a <code>ToggleButton</code> element, when <code>ToggleButton</code> is checked, I call <code>MyLooperThread</code>'s <code>init()</code> method too. </p> <pre><code>public class MyActivity extends Activity implements OnCheckedChangeListener{ … @Override protected void onCreate(Bundle savedInstanceState){ … myToggleButton.setOnCheckedChangeListener(this); myToggleButton.setChecked(true);//checked by default MyLooperThread myLooper = new MyLooperThread(); myLooper.init(); } @Override public void onCheckedChanged(CompoundButton button, boolean isChecked) { if(isChecked){ MyLooperThread myLooper = new MyLooperThread(); myLooper.init(); }else{ ... } } } </code></pre> <p>When launch my app, it is fine. My toggle button is shown as checked by default. When I uncheck it & check it again, I got <strong>exception:</strong> </p> <pre><code>java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() </code></pre> <p>which is pointed to the <code>init()</code> method's last line of code <code>MyObject obj = new MyObject(mHandler);</code></p> <p><strong>Why I got this exception?</strong> I don't understand, my <code>mHandler</code> is created after I called <code>Looper.prepare()</code> in <code>run()</code>.</p>

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