在導航抽屜上，后退按鈕無法正常工作？

Question

片段重疊

我有5個片段，無論打開多少片段，按下Back鍵我都想移到主頁片段。

如果我從

[1]-> [2]，然后按回[1]顯示的主頁片段

[1]-> [3]，然后按回[1]顯示的主頁片段

[1]-> [4]，然后按回[1]顯示的主頁片段

[1]-> [5]，然后按回[1]顯示的主頁片段

如我所願。

但是問題是

[1]-> [2]-> [3]，然后按[3]上的主片段重疊

[1]-> [2]-> [4]，然后在[4]上按回原片段重疊

[1]-> [2]-> [5]，然后按[5]上的主片段重疊

我僅將家庭片段添加到backStack並使用了replace片段方法。

為什么會這樣呢？？？

 @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.all_activity_layout); setToolbar(); addFragment(AttractionsFragment.newInstance()); setNavigationDrawer(); } @SuppressWarnings("StatementWithEmptyBody") @Override public boolean onNavigationItemSelected(MenuItem item) { switch (item.getItemId()) { case R.id.nav_attractions: if (mCurrentNavigationDrawerItem != 0) { mCurrentNavigationDrawerItem = 0; replaceFragment(AttractionsFragment.newInstance()); } break; case R.id.nav_packages: if (mCurrentNavigationDrawerItem != 1) { mCurrentNavigationDrawerItem = 1; replaceFragment(PackagesFragment.newInstance()); } break; case R.id.nav_passes: if (mCurrentNavigationDrawerItem != 2) { mCurrentNavigationDrawerItem = 2; replaceFragment(PassesFragment.newInstance()); } break; case R.id.nav_coupons: if (mCurrentNavigationDrawerItem != 3) { mCurrentNavigationDrawerItem = 3; replaceFragment(CouponsFragment.newInstance()); } break; case R.id.nav_more: if (mCurrentNavigationDrawerItem != 4) { mCurrentNavigationDrawerItem = 4; replaceFragment(MoreFragment.newInstance()); } break; } mNavigationView.getMenu().getItem(mCurrentNavigationDrawerItem).setChecked(true); DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); drawer.closeDrawer(GravityCompat.START); return true; } public void replaceFragment(Fragment fragment) { FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); // Get Current Visible fragment Fragment f = getSupportFragmentManager().findFragmentById(R.id.fragment_container); // Add to back stack only if it is AttractionsFragment if (f instanceof AttractionsFragment) { transaction.addToBackStack(fragment.getClass().getName()); } transaction.replace(R.id.fragment_container, fragment); transaction.commit(); Log.d("Navigation", "BackStack Count:" + getSupportFragmentManager().getBackStackEntryCount()); } public void addFragment(Fragment fragment) { FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); transaction.add(R.id.fragment_container, fragment, "AttractionsFragment"); transaction.commit(); } @Override public void onBackPressed() { DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); if (drawer.isDrawerOpen(GravityCompat.START)) { drawer.closeDrawer(GravityCompat.START); } else { super.onBackPressed(); } } 

Answer 1

您需要先彈出第二個片段，然后才能導航到第三個片段。

  Fragment f = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
    // Add to back stack only if it is AttractionsFragment
    if (f instanceof AttractionsFragment) {
        transaction.addToBackStack(fragment.getClass().getName());
    } else {
        activity.getSupportFragmentManager().popBackStackImmediate();
    }

    transaction.replace(R.id.fragment_container, fragment);
    transaction.commit();

Answer 2

刪除transaction.addToBackStack(fragment.getClass().getName()); 行，它將正常工作。 請檢查下面的代碼

public void replaceFragment(Fragment fragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();

// Get Current Visible fragment
Fragment f = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
// Add to back stack only if it is AttractionsFragment

transaction.replace(R.id.fragment_container, fragment);
transaction.commit();

Log.d("Navigation", "BackStack Count:" + getSupportFragmentManager().getBackStackEntryCount());


 }

Answer 3

將容器視圖替換為第一個片段：

@Override
public void onBackPressed() {

FragmentManager fm = getFragmentManager();
fm.beginTransaction().replace(R.id.fragment_container, new **your_first_fragment**()).commit();

DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
    drawer.closeDrawer(GravityCompat.START);
} else {
    super.onBackPressed();
}
}

Answer 4

如果要在同一活動中添加/啟動所有三個片段，請使用FragmentTransaction的replace（）方法（用Fragment3替換Fragment2）來代替FragmentTransaction的add（）方法來顯示Fragment3。 replace方法在添加新片段之前從后堆棧中刪除當前片段。 如果要從其他活動中啟動Fragment3，因此不想/不希望使用replace（），請在開始新活動之前從Backstack中刪除Fragment2（這會添加fragment3）：

// in Fragment2, before adding Fragment3:
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
               .remove(this) // "this" refers to current instance of Fragment2
               .commit();
fragmentManager.popBackStack();
// now go ahead and launch (add) fragment3
// if fragment3 is launched from a different activity, 
// start that activity instead
fragmentManager.beginTransaction()
               .add(R.id.a_container_view_in_activity, new Fragment3(),
                    Fargment3.FRAGMENT3_ID)
               .commit();

這樣可以解決您的問題。 嘗試這個..

Answer 5

嘗試這個：

在您的onBackPressed ：

    @Override
public void onBackPressed(){
    FragmentManager fm = getSupportFragmentManager();
    if (fm.getBackStackEntryCount() > 0) {
        Log.i("MainActivity", "popping backstack");
        fm.popBackStack();
    } else {
        Log.i("MainActivity", "nothing on backstack, calling super");
        super.onBackPressed();  
    }
}

也可以在您的替換片段中解決重疊的問題

transaction.replace(((ViewGroup)(getView().getParent())).getId(), fragment);

要么

getSupportFragmentManager().beginTransaction().replace(R.id.container,new FirstFragment()).commit(); 

嘗試在替換片段中更改代碼：

public void replaceFragment(Fragment fragment) {
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();

    // Get Current Visible fragment
    //Fragment f = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
    AttractionsFragment myFragment = (AttractionsFragment)getFragmentManager().findFragmentByTag("MY_FRAGMENT");
    if (myFragment != null && myFragment.isVisible()) {
        // Add to back stack only if it is AttractionsFragment
        transaction.addToBackStack(null);
    }
    transaction.replace(R.id.fragment_container, fragment, "MY_FRAGMENT");
    transaction.commit();

    Log.d("Navigation", "BackStack Count:" + getSupportFragmentManager().getBackStackEntryCount());

}

Answer 6

在OnBackpress添加以下代碼：

 @Override
        public void onBackPressed() {
            drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
            if (drawer.isDrawerOpen(GravityCompat.START)) {
                drawer.closeDrawer(GravityCompat.START);
            } else {
                if (getFragmentManager().findFragmentById(R.id.activity_container) instanceof HomeFragment) {
                    super.onBackPressed();
                } else {
                        replaceFragment(this, new HomeFragment());
                    }
                }

並使用下面給出的代碼在所有情況下更改您的replaceFragment和AddFragment方法：

 public void addFragment(final Activity mActivity, final Fragment newFragment, final Fragment hideFragment) {
            final FragmentManager fragmentManager = mActivity.getFragmentManager();
            final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.hide(hideFragment);
            fragmentTransaction.add(R.id.activity_container, newFragment, newFragment.getClass().getSimpleName());
            fragmentTransaction.addToBackStack(hideFragment.getClass().getSimpleName());
            fragmentTransaction.commitAllowingStateLoss();
        }
public void replaceFragment(final Activity mActivity, final Fragment newFragment) {
        final FragmentManager fragmentManager = mActivity.getFragmentManager();
        final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.activity_container, newFragment, newFragment.getClass().getSimpleName());
        fragmentTransaction.commit();
    }

其中activity_container是activity_container的xml文件中的FrameLayout ID。

在活動的onCreate ，調用replaceFragment方法而不是addFragment 。 並在所有導航項目的click事件中，調用replaceFragment方法。