按下后退按钮上的导航抽屉活动是空白活动答案

【问题标题】：Navigation drawer activity on press back button is blank Activity按下后退按钮上的导航抽屉活动是空白活动
【发布时间】：2017-04-14 03:53:46
【问题描述】：

我在导航抽屉菜单中有带有片段的导航抽屉活动。我想要的是当用户按两次后退按钮退出应用程序时。但取而代之的是空白活动。

创建方法：

 @Override
protected void onCreate(Bundle savedInstanceState) {

    if (broj == 1)    {
        startActivity(new Intent(this, Cover.class));
    }

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);

    toggle.syncState();
    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

    FragmentMainPage pocetnaFragment = new FragmentMainPage();
    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    fragmentTransaction.addToBackStack(null).replace(R.id.relativeLayoutZaFragment, pocetnaFragment, "1");

    fragmentTransaction.addToBackStack(null);
    fragmentTransaction.commit();
    fragmentTransaction.addToBackStack(null);
    // Pozivanje metode

    getSupportActionBar().setTitle("Auto magazin");

    ActionBar.LayoutParams p = new ActionBar.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
    p.gravity = Gravity.LEFT;

    view = getLayoutInflater().inflate(R.layout.action_bar, null);

    ActionBar.LayoutParams params = new ActionBar.LayoutParams(
            ActionBar.LayoutParams.WRAP_CONTENT,
            ActionBar.LayoutParams.MATCH_PARENT,
            Gravity.LEFT);

    TextView Title = (TextView) view.findViewById(R.id.actionbar_title);
    Title.setText("Auto magazin");

    getSupportActionBar().setCustomView(view,params);
    getSupportActionBar().setDisplayShowCustomEnabled(true); //show custom title
    getSupportActionBar().setDisplayShowTitleEnabled(false); //hide the default title
 // getSupportActionBar().setIcon(R.drawable.logo);
}

onBackPressed() 方法是：

boolean doubleBackToExitPressedOnce = false;

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    assert drawer != null;

    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
        return;
    }
    else if (doubleBackToExitPressedOnce) {
        super.onBackPressed();
        return;
    }

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

    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            doubleBackToExitPressedOnce = false;
        }
    }, 2000);
}

【问题讨论】：

这是因为您已将 FragmentTransaction 添加到后台堆栈。 super.onBackPressed() 调用将首先弹出该事务。如果您不想通过按后退按钮删除 Fragment，请不要将 FragmentTransaction 添加到后退堆栈中。
是的，答案是正确的。非常感谢。

标签： android

【解决方案1】：

您可以处理片段中的后退按钮单击。详情请参考this页面

【讨论】：