Android Correct Fragment BackStack

Question

我正在努力做出正确的BackStack。我试图实施this decision。但它对我不起作用。

我在导航抽屉和其他导航中有一个列表。因此，当我多次选择不同的片段列表时，我希望一键式返回主菜单而不是返回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

您可以从定义这两种方法开始：

使用标志推送片段事务的方法，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);
}

然后你只需要处理以下3种情况：

1）当新创建活动时，您不会将片段添加到backstack：

@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）如果要在导航流程中添加新片段，请调用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）如果要推送的想要的片段是DefaultHomeFragment，请清除堆栈，然后第一次添加它，如下所示：

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);
}

此代码可能会让您更好地了解：https://github.com/GrzegorzFeather/open-mbsurfer