将活动保留在堆栈中，但只返回主

Question

我有九个活动。例如，活动“A”是主要的。用户从NavigationDrawer打开活动“B”，“С”，“D”，在“D”中他点击“返回”按钮。在这种情况下，需要返回到活动“A”，而不是通过最近打开的活动的整个堆栈。

此代码做什么，我需要：

@Override 
    public boolean onNavigationItemSelected(@NonNull MenuItem item) { 
     Handler mHandler = new Handler(); 
     drawerLayout.closeDrawers(); 
     switch (item.getItemId()) { 
      case R.id.A: 
       if (item.isChecked()) { 
        break; 
       } else { 
        mHandler.postDelayed(new Runnable() { 
         @Override 
         public void run() { 
          intent = new Intent(activity, A.class); 
          intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); 
          activity.startActivity(intent); 
         } 
        }, 250); 
       } 
       break; 
      case R.id.B: 
       if (item.isChecked()) { 
        break; 
       } else { 
        if (activity instanceof A) { 
         userFlavorsMap.clear(); 
         if (flavorContainer.getChildCount() > 0){ 
          flavorContainer.removeAllViews(); 
         } 
        } 
        mHandler.postDelayed(new Runnable() { 
         @Override 
         public void run() { 
          intent = new Intent(activity, B.class); 
          intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); 
          activity.startActivity(intent); 
         } 
        }, 250); 
       } 
       break; 
      case R.id.C: 
       if (item.isChecked()) { 
        break; 
       } else { 
        if (activity instanceof A) { 
         userFlavorsMap.clear(); 
         if (flavorContainer.getChildCount() > 0){ 
          flavorContainer.removeAllViews(); 
         } 
        } 
        mHandler.postDelayed(new Runnable() { 
         @Override 
         public void run() { 
          intent = new Intent(activity, C.class); 
          intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); 
          activity.startActivity(intent); 
         } 
        }, 250); 
       } 
       break; 
      case R.id.D: 
       if (item.isChecked()) { 
        break; 
       } else { 
        if (activity instanceof A) { 
         userFlavorsMap.clear(); 
         if (flavorContainer.getChildCount() > 0){ 
          flavorContainer.removeAllViews(); 
         } 
        } 
        mHandler.postDelayed(new Runnable() { 
         @Override 
         public void run() { 
          intent = new Intent(activity, D.class); 
          intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); 
          activity.startActivity(intent); 
         } 
        }, 250); 
       } 
       break; 
      case R.id.E: 
       if (item.isChecked()) { 
        break; 
       } else { 
        if (activity instanceof A) { 
         userFlavorsMap.clear(); 
         if (flavorContainer.getChildCount() > 0){ 
          flavorContainer.removeAllViews(); 
         } 
        } 
        mHandler.postDelayed(new Runnable() { 
         @Override 
         public void run() { 
          intent = new Intent(activity, E.class); 
          intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); 
          activity.startActivity(intent); 
         } 
        }, 250); 
       } 
       break; 
      case R.id.F: 
       File usersCounter = new File("data/data/com.com.com/shared_prefs/file.xml"); 
       if (usersCounter.exists()) { 
        if (item.isChecked()) { 
         break; 
        } else { 
         if (activity instanceof A) { 
          userFlavorsMap.clear(); 
          if (flavorContainer.getChildCount() > 0){ 
           flavorContainer.removeAllViews(); 
          } 
         } 
         mHandler.postDelayed(new Runnable() { 
          @Override 
          public void run() { 
           intent = new Intent(activity, F.class); 
           intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); 
           activity.startActivity(intent); 
          } 
         }, 250); 
        } 
        break; 
       } else { 
        if (item.isChecked()) { 
         break; 
        } else { 
         if (activity instanceof A) { 
          userFlavorsMap.clear(); 
          if (flavorContainer.getChildCount() > 0){ 
           flavorContainer.removeAllViews(); 
          } 
         } 
         mHandler.postDelayed(new Runnable() { 
          @Override 
          public void run() { 
           intent = new Intent(activity, G.class); 
           intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); 
           activity.startActivity(intent); 
          } 
         }, 250); 
        } 
        break; 
       } 
     } 
     return false; 
    } 

但是，如果用户切换到活动，例如，“C”和折叠的应用程序，然后返回到应用程序后，会打开“A”。我怎样才能完成代码，以便当我返回到应用程序时，它打开上次打开的Activity，但所有最近的活动都不会在堆栈中？

在manifect 机器人：launchMode =“singleTop”

Answer 1

尝试这种在每个活动除了MainActivity

@Override 
    public void onBackPressed() { 
     super.onBackPressed(); 
     Intent mainIntent = new Intent(YourCurrentActivityName.this,MainActivity.class); 
     startActivity(mainIntent); 
     finish(); 
    }