如何在应用未激活时跟踪onKeyDown事件？

Question

我想为Volume up键添加一个按钮单击事件处理程序，并在用户连续三次单击该音量时启动一个活动。以下代码仅在我的应用程序的主要活动处于活动状态时有效。应用程序未处于活动状态时如何捕获onKeyDown？

@Override
public boolean onKeyDown (int KeyCode, KeyEvent event){

//listen if VOLUME UP BUTTON IS PRESSED
    if(KeyCode == KeyEvent.KEYCODE_VOLUME_UP){
        //increase the value of vBtnClicked by 1 each time it is clicked.
        vBtnClicked++;
        //if btn is clicked 3 times excecute code and reset the value of 
//vBtnClicked
        if(vBtnClicked == 3){
            //reset value of variable for later use.
            vBtnClicked = 0;
            //MY CODE WILL BE ADDED HERE
            Toast.makeText(getBaseContext(), "dummy_text" , 
Toast.LENGTH_SHORT).show();

        }Log.d("log_dave","backclick value is:" + vBtnClicked);
        return true;
    }
    //this following code is if you want the code to execute only after the 
//button is pressed 3 times in a row.
    //if another button is pressed in between vBtnCliced is reset
    else {
        vBtnClicked=0;
    }

    return super.onKeyDown(KeyCode, event);
 }