Android App: 按键识别

Android app监听普通的按键有两种方式:

实现Activity的onKeyDown方法

public class Android_game extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_android_game);
    }
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK){
                Intent i = new Intent(this,Android_game_menu.class);
                startActivity(i);
        } 
        return false;
    }
}

实现OnClickListener接口的方式

public class MyActivity extends Activity implementsOnClickListener {
    // ...
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.about_button:
                Intent i = new Intent(this, About.class);
                startActivity(i);
                break;
    // More buttons go here (if any) ...
        }
    }
}

Android app Home Key的监听方式:

对于Home键的监听不是那么容易,因为Home键可以将程序退出放在后台,所以这个事件是直接分发给系统,系统接收到之后做相应处理,Home键的事件不是直接传递到应用里面.所以在上述监听一般的按键(比如volume key等)的代码中,相应的回调中是收不到Home键的事件的.
对Home键的监听主要通过注册广播接收器实现,拦截让窗口关闭的系统动作,然后根据Intent里面的具体参数,分析当前到底是Home键, 应用切换键,还是其他功能按键.

public class HomeWatcherReceiver extends BroadcastReceiver {
    private static final String LOG_TAG = "HomeReceiver";
    private static final String SYSTEM_DIALOG_REASON_KEY = "reason";
    private static final String SYSTEM_DIALOG_REASON_RECENT_APPS = "recentapps";
    private static final String SYSTEM_DIALOG_REASON_HOME_KEY = "homekey";
    private static final String SYSTEM_DIALOG_REASON_LOCK = "lock";
    private static final String SYSTEM_DIALOG_REASON_ASSIST = "assist";

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        Log.i(LOG_TAG, "onReceive: action: " + action);
        if (action.equals(Intent.ACTION_CLOSE_SYSTEM_DIALOGS)) {
            // android.intent.action.CLOSE_SYSTEM_DIALOGS
            String reason = intent.getStringExtra(SYSTEM_DIALOG_REASON_KEY);
            Log.i(LOG_TAG, "reason: " + reason);

            if (SYSTEM_DIALOG_REASON_HOME_KEY.equals(reason)) {
                // 短按Home键
                Log.i(LOG_TAG, "homekey");

            }
            else if (SYSTEM_DIALOG_REASON_RECENT_APPS.equals(reason)) {
                // 长按Home键 或者 activity切换键
                Log.i(LOG_TAG, "long press home key or activity switch");

            }
            else if (SYSTEM_DIALOG_REASON_LOCK.equals(reason)) {
                // 锁屏
                Log.i(LOG_TAG, "lock");
            }
            else if (SYSTEM_DIALOG_REASON_ASSIST.equals(reason)) {
                // samsung 长按Home键
                Log.i(LOG_TAG, "assist");
            }
        }
    }

}

注意不同手机的按键不同,所以需要对不同理由做区分.
Home键监听广播注册:
广播接收器的注册有两种方式,一种是静态注册,即写在manifest里面声明;另一种是动态注册,即在Java代码里面注册.
上面对Home键实现监听的这个receiver的静态注册如下:

        <receiver android:name="com.mengdd.hellohome.HomeWatcherReceiver" >
            <intent-filter>
                <action android:name="android.intent.action.CLOSE_SYSTEM_DIALOGS" />
            </intent-filter>
        </receiver>

但是发现静态注册不起作用,即收不到onReceive回调??
采用动态注册:

    private static HomeWatcherReceiver mHomeKeyReceiver = null;

    private static void registerHomeKeyReceiver(Context context) {
        Log.i(LOG_TAG, "registerHomeKeyReceiver");
        mHomeKeyReceiver = new HomeWatcherReceiver();
        final IntentFilter homeFilter = new IntentFilter(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);

        context.registerReceiver(mHomeKeyReceiver, homeFilter);
    }

    private static void unregisterHomeKeyReceiver(Context context) {
        Log.i(LOG_TAG, "unregisterHomeKeyReceiver");
        if (null != mHomeKeyReceiver) {
            context.unregisterReceiver(mHomeKeyReceiver);
        }
    }

在Activity的onResume和onPause里面分别调用:

    @Override
    protected void onResume() {
        super.onResume();

        registerHomeKeyReceiver(this);
    }

    @Override
    protected void onPause() {
        unregisterHomeKeyReceiver(this);
        super.onPause();
    }

当然也可以根据需要在其他合适的时机注册和注销.