How to listen for a key press in Android

I want to listen for an Android key press. For example when I press the Menu key on the phone, I will get this key press and start an application.

And I don't know in Phonewindowmanager.java when I pressed a key, t开发者_Python百科he interceptKeyTq() come to twice.

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_MENU) {
            //do something
        }
        return true;
    }

Hope this helps.

Here is a simple test program. don't forget setFocusable(true) and invalidate().

Insted of using System.out, you can use Log - http://code.google.com/android/reference/android/util/Log.html

public class HelloAndroid extends Activity {
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(new MyView(this));
    }

    class MyView extends View {
        private static final String LOGID = "MxView";
        String message = "No key pressed yet.";

        MyView(Context context) {
                super(context);
                setFocusable(true);
        }

        @Override
        protected void onDraw(Canvas canvas) {
                Paint paint = new Paint();
                canvas.drawText(message, 5, 20, paint);
        }

        @Override
        public boolean onKeyDown(int keyCode, KeyEvent ev) {
                switch(keyCode) {
                case KeyEvent.KEYCODE_DPAD_UP:
                        message = "Key Up!";
                        Log.i(LOGID, message);
                        break;
                case KeyEvent.KEYCODE_DPAD_DOWN:
                        message = "Key Down!";
                        Log.i(LOGID, message);
                        break;
                default:
                        return false;
                }
                invalidate();
                return true;
        }
    }

}