Android 回调机制

Android 回调机制

/**
* Interface definition for a callback to be invoked when a view is clicked.
*/
public interface OnClickListener {
/**
* Called when a view has been clicked.
*
* @param v The view that was clicked.
*/
void onClick(View v);
}

public class MainActivity extends Activity implements OnClickListener {
Button btn_location;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

btn_location = (Button) findViewById(R.id.btn_location);
btn_location.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {
//TODO action
}
});
}
}

public class View implements Drawable.Callback, KeyEvent.Callback,
AccessibilityEventSource {
/**
* Listener used to dispatch click events.
* This field should be made private, so it is hidden from the SDK.
* {@hide}
*/
public OnClickListener mOnClickListener;

/**
* Register a callback to be invoked when this view is clicked. If this view is not
* clickable, it becomes clickable.
*
* @param l The callback that will run
*
* @see #setClickable(boolean)
*/
public void setOnClickListener(OnClickListener l) {
if (!isClickable()) {
setClickable(true);
}
getListenerInfo().mOnClickListener = l;
}

/**
* Call this view's OnClickListener, if it is defined.  Performs all normal
* actions associated with clicking: reporting accessibility event, playing
* a sound, etc.
*
* @return True there was an assigned OnClickListener that was called, false
*         otherwise is returned.
*/
public boolean performClick() {
sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);

ListenerInfo li = mListenerInfo;
if (li != null && li.mOnClickListener != null) {
playSoundEffect(SoundEffectConstants.CLICK);
li.mOnClickListener.onClick(this);
return true;
}

return false;
}
}