正確的方法來做片段transacrtion

Question

我正在開發一個活動和多個片段的android應用程序。我的應用包含導航抽屜。它的佈局包含listview。點擊它的項目，我用ft.replace(R.id.my_placehodler, new MyFragment())動態地改變片段，並將交易添加到backstack ft.addToBackstack(null)。當我每次創建新的事務時都會創建新的事務。在我看來，這不是一個好方法。你能否給我提供關於進行片段交易的正確方法的建議？

Answer 1

只需調用setFragment(FragmentClassObject,false,"fragment");方法即可。

public void setFragment(Fragment fragment, boolean backStack, String tag) { 
    manager = getSupportFragmentManager(); 
    fragmentTransaction = manager.beginTransaction(); 
    if (backStack) { 
     fragmentTransaction.addToBackStack(tag); 
    } 
    fragmentTransaction.replace(R.id.content_frame, fragment, tag); 
    fragmentTransaction.commit(); 
} 

Answer 2

如果你想避免instanciating多個實例同一類片段的，那是你想擁有每類片段的單個實例，您可以通過使用標籤識別每個片段。

@Override 
public void onNavigationDrawerItemSelected(int position) { 
    String tag = ""; 
    switch (position) { 
    case 0: 
     tag = "fragment_0"; 
     break; 
    case 1: 
     tag = "fragment_1"; 
     break; 
    case 2: 
     tag = "fragment_2"; 
     break; 
    } 

    FragmentManager fragmentManager = getFragmentManager(); 
    Fragment fragment = fragmentManager.findFragmentByTag(tag); 
    if (fragment == null) { 
     // Only in case there is no already instaciated one, 
     // a new instance will be instanciated. 
     switch (position) { 
     case 0: 
      fragment = new Fragment_class_0(); 
      break; 
     case 1: 
      fragment = new Fragment_class_1(); 
      break; 
     case 2: 
      fragment = new Fragment_class_2(); 
      break; 
     } 
    } 

    fragmentManager.beginTransaction().replace(R.id.container, fragment, tag).commit(); 
}