在加载ANDROID后不要重新加载片段

在我的

Android

应用程序中，我有6个片段，单击导航抽屉中的项目时，这些片段会被一一替换。我的问题是，当单击导航抽屉项目时，片段会一次又一次地被加载。我不希望我的碎片一次又一次地重新加载。相反，我希望它们在从一个片段切换到另一个片段时保持以前的状态

Addbacktostack（）

不起作用。请告诉我其他方法：

我的代码是：

 @Override
public void onDrawerItemSelected(View view, int position) {
    row_view = view;
    displayView(position);

}

private void displayView(int position) {
    Fragment fragment = null;
    String title = getString(R.string.app_name);
    switch (position) {
        case 0:
            fragment = new Fragmenta();
            title = "aaaa";
            toolbar_title.setText(title);
            break;
        case 1:
            fragment = new Fragmentb();
            title = "Introduction";
            toolbar_title.setText(title);
            break;
        case 2:
            fragment = new Glossary();
            title = "Glossary";
            toolbar_title.setText(title);
            break;
        case 3:
            fragment = new SettingsFragment();
            title = "Settings";
            toolbar_title.setText(title);
            break;
        case 4:
            fragment = new FeedbackFragment();
            title = "Feedback";
            toolbar_title.setText(title);
            break;
        case 5:
            fragment = new Fragmentc();
            title = "cc";
            toolbar_title.setText(title);
            break;

        default:
            break;
    }



if (myfragmentstate != null) {             // This is always null
        //Restore the fragment's instance
        fragment = getSupportFragmentManager().getFragment(myfragmentstate, "mContent");
        Log.i("sadfas","fragment"+fragment);

    }
    if (fragment != null) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager
                .beginTransaction();
        fragmentTransaction.replace(R.id.container_body,fragment);   //always reloads a fragment and i donot want this
        fragmentTransaction.commit();
        toolbar_title.setText(title);

    }
}



@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    Log.i("MicroRAE","instanmce save"+fragment);
    getSupportFragmentManager().putFragment(outState, "mContent", fragment);
}

---

我找到的最佳解决方案如下：

onSavedInstanceState（）：当活动要关闭时（将活动从一个移动到另一个或配置更改），始终在片段内调用。因此，如果我们在同一活动上调用多个片段，那么我们必须使用以下方法：

使用片段的OnDestroyView（）并将整个对象保存在该方法中。然后OnActivityCreated（）：检查对象是否为null（因为此方法每次都调用）。现在在这里恢复一个对象的状态

它总是有用的

要正确保存片段的实例状态，应执行以下操作：

在片段中，通过重写onSaveInstanceState（）保存实例状态，并在onActivityCreated（）中还原：

}

重要的一点是，在活动中，必须将片段的实例保存在onSaveInstanceState（）中，并在onCreate（）中还原

---

希望这有帮助。

我找到了一个非常好的解决方案：

String backStateName = fragment.getClass().getName();

    FragmentManager fragmentManager = getSupportFragmentManager();
    boolean fragmentPopped = fragmentManager.popBackStackImmediate (backStateName, 0);

    if (!fragmentPopped){ //fragment not in back stack, create it.
        FragmentTransaction fragmentTransaction = fragmentManager
                .beginTransaction();
        fragmentTransaction.replace(R.id.container_body,fragment);
        fragmentTransaction.addToBackStack(backStateName);
        fragmentTransaction.commit();
        toolbar_title.setText(title);
    }

---

非常简单：只需声明一个全局字符串，保存最后加载的片段。在加载片段的方法中，只要比较是否相同即可。如果不匹配，则加载新片段，如果匹配，则不执行任何操作

     String lastFragmentLoaded = null; // THIS VARIABLE IS GLOBAL

        //YOUR METHOD THAT LOAD FRAGMENTS
        LoadMyFragment() 
   {
             String currentFragmentName = yourFragment.getClass().getName();

             if(lastFragmentLoaded != currentFragmentName) {
                   //LOAD YOUR FRAGMENTS

             //FINALLY, SAVE YOUR LAST FRAGMENT LOADED TO COMPARE NEXT TIME
             lastFragmentLoaded = currentFragmentName;
        }
        else 
        {
            // LET IT EMPTY IF YOU WANT
        }
   }

---

我必须在片段和活动中保存状态吗？SaveInstanceState在活动中始终为空？？请编辑您的问题以显示您所做的更改@Shivanigupta请建议我下一步要做什么

String backStateName = fragment.getClass().getName();

    FragmentManager fragmentManager = getSupportFragmentManager();
    boolean fragmentPopped = fragmentManager.popBackStackImmediate (backStateName, 0);

    if (!fragmentPopped){ //fragment not in back stack, create it.
        FragmentTransaction fragmentTransaction = fragmentManager
                .beginTransaction();
        fragmentTransaction.replace(R.id.container_body,fragment);
        fragmentTransaction.addToBackStack(backStateName);
        fragmentTransaction.commit();
        toolbar_title.setText(title);
    }

     String lastFragmentLoaded = null; // THIS VARIABLE IS GLOBAL

        //YOUR METHOD THAT LOAD FRAGMENTS
        LoadMyFragment() 
   {
             String currentFragmentName = yourFragment.getClass().getName();

             if(lastFragmentLoaded != currentFragmentName) {
                   //LOAD YOUR FRAGMENTS

             //FINALLY, SAVE YOUR LAST FRAGMENT LOADED TO COMPARE NEXT TIME
             lastFragmentLoaded = currentFragmentName;
        }
        else 
        {
            // LET IT EMPTY IF YOU WANT
        }
   }