Android 正确的片段 BackStack

Question

我正在尝试做一个正确的 BackStack。我已经尝试实现 this decision。但这对我不起作用。

我在导航抽屉和其他导航中有一个列表。所以，当我 select 不同的片段列表几次时，我希望 one-touch return 到主菜单而不是 returning 到 BackStack.

@Override
public void onBackPressed() {
    if (getSupportFragmentManager().getBackStackEntryCount() == 1){
        finish();
    }
    else {
        super.onBackPressed();
    }
}


@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt("theme", mThemeId);
}
private void replaceFragment (Fragment fragment){
    String backStateName =  fragment.getClass().getName();
    String fragmentTag = backStateName;

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

    if (!fragmentPopped && manager.findFragmentByTag(fragmentTag) == null) {
        FragmentTransaction ft = manager.beginTransaction();
        ft.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_right,
                R.anim.slide_back_in_left, R.anim.slide_back_out_right);
        ft.replace(R.id.frgmCont, fragment);
        ft.addToBackStack(backStateName);
        ft.commit();
    }


}

Answer 1

您可以从定义这两个方法开始：

一种推送带有标志的片段事务的方法，该标志定义是否应将片段添加到 backStack：

private void pushToStack(Fragment fragment, String tag, int transition, boolean addToBackStack){
    FragmentManager fm = this.getSupportFragmentManager();

    FragmentTransaction transaction = fm.beginTransaction();
    transaction.replace(R.id.container, fragment, tag);

    if(transition > 0){
        transaction.setTransition(transition);
    }
    if(addToBackStack){
        transaction.addToBackStack(tag);
    }

    transaction.commit();
}

清除backStack的方法：

public void clearStack(){
    FragmentManager fm = this.getSupportFragmentManager();
    fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
}

那么你只需要处理以下3种情况：

1) 当 activity 是新创建的，你不会将片段添加到后台堆栈：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.activity_home);
    this.pushToStack(DefaultHomeFragment.newInstance(), DefaultHomeFragment.class.getSimpleName(), -1, false);
}

2) 当您想要向导航流中添加新片段时，您调用 pushToStack 方法并将 addToBackStack 设置为 true:

this.pushToStack(NavigationSecondFragment.newInstance(), NavigationSecondFragment.class.getSimpleName(), DEFAULT_TRANSITION, true);
this.pushToStack(NavigationSecondFragment.newInstance(), NavigationThirdFragment.class.getSimpleName(), DEFAULT_TRANSITION, true);

3) 如果要推送的片段是 DefaultHomeFragment，清空堆栈，然后像这样第一次添加它：

private static final String DEFAULT_CONTENT_NAME = DefaultHomeFragment.class.getSimpleName();

public addFragmentToNavigation(Fragment newFragment){
    boolean addToBackStack = true;

    if(newFragment..getClass().getSimpleName().equals(DEFAULT_CONTENT_NAME)){
        addToBackStack = false;
        this.clearStack();
    }

    this.pushToStack(newFragment, newFragment.getClass().getSimpleName(),
        DEFAULT_TRANSITION, addToBackStack);
}

此代码可能会给您一个更好的主意：https://github.com/GrzegorzFeather/open-mbsurfer

Android 正确的片段 BackStack

Android Correct Fragment BackStack

android

android-fragments

back-stack