深入Android线程的相关问题解惑

public class ActivityDemo extends Activity {    private static final String TAG = "ActivityDemo";    private Handler mMainHandler = new Handler(new Handler.Callback() { public boolean handleMessage(Message msg) {     dumpThreadInfo();     return false; }    });    @Override    protected void onCreate(Bundle savedInstanceState) { dumpThreadInfo(); super.onCreate(savedInstanceState); // add four buttons LinearLayout layout = new LinearLayout(getApplication()); layout.setOrientation(LinearLayout.VERTICAL); Button startService = new Button(getApplication()); startService.setText("Start a Service"); startService.setOnClickListener(new View.OnClickListener() {     public void onClick(View v) {  Intent i = new Intent(getApplication(), ServiceDemo.class);  startService(i);     } }); layout.addView(startService); Button startAnother = new Button(getApplication()); startAnother.setText("Start another Activity"); startAnother.setOnClickListener(new View.OnClickListener() {     public void onClick(View v) {  Intent i = new Intent(getApplication(), AnotherActivity.class);  startService(i);     } }); layout.addView(startAnother); Button startContentProvider = new Button(getApplication()); startContentProvider.setText("Start a ContentProvider"); startContentProvider.setOnClickListener(new View.OnClickListener() {     public void onClick(View v) {  getContentResolver().query(ContentProviderDemo.CONTENT_URI, null, null, null, null);     } }); layout.addView(startContentProvider); Button startReceiver = new Button(getApplication()); startReceiver.setText("Start a BroadcastReceiver"); startReceiver.setOnClickListener(new View.OnClickListener() {     public void onClick(View v) {  Intent i = new Intent("android.action.start_broadcastreceiver_demo");  sendBroadcast(i);     } }); layout.addView(startReceiver); setContentView(layout); mMainHandler.sendEmptyMessageDelayed(0, 500);    }    public void dumpThreadInfo() { Thread.dumpStack(); Log.e(TAG, Thread.currentThread().toString()); Log.e(TAG, " " + getMainLooper());    }}