Question

我有3个活动第一个是登录第二是登记底部导航的第三个家庭活动（Bottom_nav），有3个片段A，B，C。

登录活动是启动器活动。

在登录用户中已经登录或未登录如果用户未登录，则重定向到注册活动除此之外，还可以进行家庭活动。

我已经在家庭活动中实现了onBackPressed（）但是在双击返回按钮活动时暂停并恢复。

这是我的代码：

 boolean doubleBackToExitPressedOnce = false;

@Override
public void onBackPressed() {
    if (doubleBackToExitPressedOnce) {
        super.onBackPressed();
        Bottom_nav.this.finish();
        return;
    }

    this.doubleBackToExitPressedOnce = true;
    Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();

    new Handler().postDelayed(new Runnable() {

        @Override
        public void run() {
            doubleBackToExitPressedOnce=false;
        }
    }, 2000);
}




private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.navigation_home:
                getSupportFragmentManager().beginTransaction().replace(R.id.MainFrame, new HomeFragment()).commit();
                return true;
            case R.id.navigation_dashboard:
                getSupportFragmentManager().beginTransaction().replace(R.id.MainFrame, new ProfileFragment()).addToBackStack(null).commit();
                return true;
            case R.id.navigation_notifications:
                getSupportFragmentManager().beginTransaction().replace(R.id.MainFrame, new NotificationFragment()).addToBackStack(null).commit();
                return true;
        }
        return false;
    }
};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_bottom_nav);

    getSupportFragmentManager().beginTransaction().add(R.id.MainFrame, new HomeFragment()).commit();
    BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
    navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);

}

这是日志

V/FA: Recording user engagement, ms: 2650
V/FA: Activity paused, time: 132340044
D/FA: Logging event (FE): user_engagement(_e), 
Bundle[{firebase_event_origin(_o)=auto, engagement_time_msec(_et)=2650, 
firebase_screen_class(_sc)=Bottom_nav, 
firebase_screen_id(_si)=-4687850249260059972}]
D/FA: Logging event (FE): screen_view(_vs), 
Bundle[{firebase_event_origin(_o)=auto, 
firebase_previous_class(_pc)=Bottom_nav, 
firebase_previous_id(_pi)=-4687850249260059972, 
firebase_screen_class(_sc)=RegisterPhoneActivity, 
firebase_screen_id(_si)=-4687850249260059974}]
V/FA: onActivityCreated
V/FA: Activity resumed, time: 132340054
V/FA: Screen exposed for less than 1000 ms. Event not sent. time: 184
V/FA: Activity paused, time: 132340135
D/FA: Logging event (FE): screen_view(_vs), 
Bundle[{firebase_event_origin(_o)=auto, 
firebase_previous_class(_pc)=RegisterPhoneActivity, 
firebase_previous_id(_pi)=-4687850249260059974, 
firebase_screen_class(_sc)=Bottom_nav, 
firebase_screen_id(_si)=-4687850249260059971}]
V/FA: Activity resumed, time: 132340244
W/PathParser: Points are too far apart 4.000000000000002
Points are too far apart 4.000000000000002
W/PathParser: Points are too far apart 4.000002058290173
Points are too far apart 4.000002058290173
W/PathParser: Points are too far apart 4.000001624254724
W/PathParser: Points are too far apart 4.000002923700373
Points are too far apart 4.000002923700373
W/PathParser: Points are too far apart 4.00000093640932
V/FA: Inactivity, disconnecting from the service

我要去哪里错了？我没有发现与此相关的任何问题

Answer 1

请使用这个。

boolean doubleBackToExitPressedOnce = false;
@Override
public void onBackPressed() {
    if (!doubleBackToExitPressedOnce){
        this.doubleBackToExitPressedOnce = true;
        Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                doubleBackToExitPressedOnce = false;
            }
        }, 2000);


    }else {
        if (getSupportFragmentManager().getBackStackEntryCount() != 0) {
            getSupportFragmentManager().popBackStack();
        } else {
            super.onBackPressed();
            finish();
        }

    }
}

打开片段时，您必须使用

getSupportFragmentManager().beginTransaction().replace(R.id.MainFrame, new HomeFragment()).addToBackStack(null).commit();

Answer 2

检查SupportFragmentManager的堆栈的状态可能更常见：

@Override
public void onBackPressed() {
    if (getSupportFragmentManager().getBackStackEntryCount() != 0) {
        getSupportFragmentManager().popBackStack();
    } else {

        /* only consider those clicks when there is no stack left */
    }
}

否则，您的自定义功能将破坏SupportFragmentManager的行为。

Answer 3

Bottom_nav.this.finish();上实际上发生了什么？如果不是结束活动声明，请尝试：

@Override
public void onBackPressed() {
    if (doubleBackToExitPressedOnce && (!isFinishing() || !isDestroyed())) {
        finish();
        //super.onBackPressed();
        Bottom_nav.this.finish();
        return;
    }
    //...
}

Answer 4

如果启动器屏幕为登录状态，则使用finishAffinity()方法将完成当前活动和所有父活动，但仅在Android 4.1或更高版本中有效。

if (doubleBackToExitPressedOnce) {
    super.onBackPressed();
    Bottom_nav.this.finishAffinity();
    return;
}

如果您不想在片段中回溯，请使用它。

FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.container_body, fragment);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commit();

或者您可以通过

    getSupportFragmentManager().beginTransaction().replace(R.id.MainFrame, new HomeFragment()).addToBackStack(null).commit();

onBackPressed（）应用程序未关闭

4 个答案: