Android监听返回键、Home键+再按一次返回键退出应用

Android监听返回键需重写onKeyDown()方法

Home键keyCode==KeyEvent.KEYCODE_HOME

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
            //++自己定义点击事件
            return true;//不运行父类的点击事件
        }
        return super.onKeyDown(keyCode, event);//继续运行父类的其它点击事件   
    }

实例：再按一次返回键退出应用

private long exitTime = 0;

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){   
        if((System.currentTimeMillis()-exitTime) > 2000){  
            Toast.makeText(getApplicationContext(), "再按一次退出应用", Toast.LENGTH_SHORT).show();                                
            exitTime = System.currentTimeMillis();   
        } else {
            finish();
            System.exit(0);
        }
        return true;   
    }
    return super.onKeyDown(keyCode, event);
}