Android 再按一次退出程序的实现方法

第一种（handler+标志位）

private boolean isexit;
    private handler handler;
    @override
    protected void oncreate(bundle savedinstancestate) {
        super.oncreate(savedinstancestate);
        setcontentview(r.layout.activity_main);
        handler = new handler(){
            @override
            public void handlemessage(message msg) {
                super.handlemessage(msg);
                isexit = false;
            }
        };
    }
　　public boolean onkeydown(int keycode, keyevent event) {
        if(keycode==keyevent.keycode_back){
            if(!isexit){
                isexit = true;
                handler.sendemptymessagedelayed(0, 1500);
                toast.maketext(this, "再按一次推出程序", 1000).show();
                return false;
            }else{
                finish();
            }
        }
        return super.onkeydown(keycode, event);
    }

第二种（记录点击的时间）

private long exittimemillis = system.currenttimemillis();
    @override
    protected void oncreate(bundle savedinstancestate) {
        super.oncreate(savedinstancestate);
        setcontentview(r.layout.activity_main);
    }

    @override
    public boolean onkeydown(int keycode, keyevent event) {
        if(keycode==keyevent.keycode_back){
            long currenttime = system.currenttimemillis();
            if(currenttime-exittimemillis==0||currenttime-exittimemillis>1500){
                exittimemillis = system.currenttimemillis();
                toast.maketext(this, "再按一次推出程序", 1000).show();
                return false;
            }else{
                finish();
            }
        }
        return super.onkeydown(keycode, event);
    }