android返回键退出提示的两种方法

本文提供了两种触摸返回键提示退出的两种方法

1.触摸返回键弹出对话框

public void onBackPressed(){        //android 2.0以上的 <a target=_blank href="http://blog.csdn.net/u010717419/article/details/24481537">点击解释为什么</a>
        Toast.makeText(this, "你点击了返回键", Toast.LENGTH_LONG).show();
        AlertDialog.Builder builder = new Builder(this);
        builder.setTitle("提示");
        builder.setMessage("确认要退出吗");

        builder.setPositiveButton("确认", new OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                finish();
            }
        });
        builder.setNegativeButton("取消", new OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                //不做任何动作
            }
        });

        builder.create().show();
     }

private long currentBackPressedTime = 0;
    private static final int BACK_PRESSED_INTERVAL = 2000;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void onBackPressed(){
            //1.当前的获取的毫秒数-预定值（0）肯定大于2s  //4.当下次再按时当前值跟赋予后的设定值比较
        if(System.currentTimeMillis() - currentBackPressedTime > BACK_PRESSED_INTERVAL){
            //2.把当前的毫秒数赋予预定值
            currentBackPressedTime = System.currentTimeMillis() ; 
            //3.弹出框
            Toast.makeText(this, "再按一次退出", 0).show();
        }else{
            //若当前值-设定值<2s 则执行:
            finish();
        }
    }