@Override
public void onAttachedToWindow() {
  this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);
  super.onAttachedToWindow();
}

if (keyCode == KeyEvent.KEYCODE_HOME) {
  //在这里发送一个广播出去
}

private boolean isTesting = true;
class CatchLogThread extends Thread {
  @Override
  public void run() {
    Process mLogcatProc = null;
    BufferedReader reader = null;
    String line;
    while (isTesting) {
      try {
        // 获取logcat日志信息
        mLogcatProc = Runtime.getRuntime().exec(new String[] { "logcat", "ActivityManager:I *:S" });
        reader = new BufferedReader(new InputStreamReader(mLogcatProc.getInputStream()));
        while ((line = reader.readLine()) != null) {
          if (line.indexOf("android.intent.category.HOME") > 0) {
            isTesting = false;
            handler.sendMessage(handler.obtainMessage());
            Runtime.getRuntime().exec("logcat -c");//删除日志
            break;
          }
        }
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }
};
Handler handler = new Handler() {
  public void handleMessage(android.os.Message msg) {
    Log.i(TAG,"Home key press");
    //do something here
  };
};