带有片段的导航栏

我有一个标签式动作条/ viewpager布局三个标签说一，乙，和Ç。在标签Ç标签（片段），我加入另一片段发言权片段d。与

 DFragment f= new DFragment();
 ft.add(android.R.id.content, f, "");
 ft.remove(CFragment.this);
 ft.addToBackStack(null);
 ft.commit();

我在DFragment的onResume中修改操作栏以添加按钮：

ActionBar ab = getActivity().getActionBar();
ab.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
ab.setDisplayHomeAsUpEnabled(true);
ab.setDisplayShowHomeEnabled(true);

现在在DFragment中，当我按硬件（电话）“后退”按钮时，我返回到原始的Tabbed（ABC）布局，并选择了CFragment。如何通过操作栏上按钮实现此功能？

实现OnBackStackChangedListener此代码并将其添加到您的Fragment Activity。

@Override
public void onCreate(Bundle savedInstanceState) {
    //Listen for changes in the back stack
    getSupportFragmentManager().addOnBackStackChangedListener(this);
    //Handle when activity is recreated like on orientation Change
    shouldDisplayHomeUp();
}

@Override
public void onBackStackChanged() {
    shouldDisplayHomeUp();
}

public void shouldDisplayHomeUp(){
   //Enable Up button only  if there are entries in the back stack
   boolean canGoBack = getSupportFragmentManager().getBackStackEntryCount()>0;
   getSupportActionBar().setDisplayHomeAsUpEnabled(canGoBack);
}

@Override
public boolean onSupportNavigateUp() {
    //This method is called when the up button is pressed. Just the pop back stack.
    getSupportFragmentManager().popBackStack();
    return true;
}

我知道了。只需在托管活动中覆盖onOptionsItemSelected并弹出后退栈，例如

public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home: {
            FragmentManager fm = getSupportFragmentManager();
            if (fm.getBackStackEntryCount() > 0) {
                fm.popBackStack();
                return true;
            }
            break;
        }
    }
    return super.onOptionsItemSelected(item);
}

呼叫getActionBar().setDisplayHomeAsUpEnabled(boolean);并getActionBar().setHomeButtonEnabled(boolean);在onBackStackChanged()如下的答案解释。

如果您有一个家长活动，并且希望此向上按钮用作后退按钮，则可以使用以下代码：

将此添加到您的主活动类中的onCreate

getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
        @Override
        public void onBackStackChanged() {
            int stackHeight = getSupportFragmentManager().getBackStackEntryCount();
            if (stackHeight > 0) { // if we have something on the stack (doesn't include the current shown fragment)
                getSupportActionBar().setHomeButtonEnabled(true);
                getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            } else {
                getSupportActionBar().setDisplayHomeAsUpEnabled(false);
                getSupportActionBar().setHomeButtonEnabled(false);
            }
        }

    });

然后像这样添加onOptionsItemSelected：

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            getSupportFragmentManager().popBackStack();
            return true;
     ....
 }

我通常一直都用这个，看起来很合法

您可以使用向上按钮像返回按钮一样返回;

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            super.onBackPressed();
            return true;
    }
    return super.onOptionsItemSelected(item);
}

我知道这个问题很旧，但也许有人（像我一样）也需要它。

如果您的Activity扩展了AppCompatActivity，则可以使用更简单的（两步）解决方案：

1-每当您添加非本地片段时，只需在提交片段事务之后立即显示向上按钮即可。像这样：

    // ... add a fragment
    // Commit the transaction
    transaction.commit();

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

2-然后按UP按钮，将其隐藏。

@Override
public boolean onSupportNavigateUp() {
    getSupportActionBar().setDisplayHomeAsUpEnabled(false);        
    return true;
}

而已。

我结合了Roger Garzon Nieto和sohailaziz的答案。我的应用程序只有一个MainActivity，并且片段A，B，C已加载到其中。我的“ home”片段（A）实现了OnBackStackChangedListener，并检查backStack的大小；如果小于1，则隐藏UP按钮。片段B和C总是加载后退按钮（在我的设计中，B从A启动，而C从B启动）。MainActivity本身只是在按下UP按钮时弹出后退堆栈，并具有显示/隐藏按钮的方法，这些片段称为：

主要活动：

public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        // Respond to the action bar's Up/Home button
        case android.R.id.home:
            getSupportFragmentManager().popBackStack();
            return true;
    }
    return super.onOptionsItemSelected(item);
}

public void showUpButton() { getSupportActionBar().setDisplayHomeAsUpEnabled(true); }
public void hideUpButton() { getSupportActionBar().setDisplayHomeAsUpEnabled(false); }

fragmentA（实现FragmentManager.OnBackStackChangedListener）：

public void onCreate(Bundle savedinstanceSate) {
    // listen to backstack changes
    getActivity().getSupportFragmentManager().addOnBackStackChangedListener(this);

    // other fragment init stuff
    ...
}

public void onBackStackChanged() {
    // enable Up button only  if there are entries on the backstack
    if(getActivity().getSupportFragmentManager().getBackStackEntryCount() < 1) {
        ((MainActivity)getActivity()).hideUpButton();
    }
}

片段B，片段C：

public void onCreate(Bundle savedinstanceSate) {
    // show the UP button
    ((MainActivity)getActivity()).showUpButton();

    // other fragment init stuff
    ...
}

这对我有用。覆盖onSupportNavigateUp和onBackPressed（例如，Kotlin中的代码）；

override fun onBackPressed() {
    val count = supportFragmentManager.backStackEntryCount
    if (count == 0) {
        super.onBackPressed()
    } else {
        supportFragmentManager.popBackStack()
    }
}

override fun onSupportNavigateUp(): Boolean {
    super.onSupportNavigateUp()
    onBackPressed()
    return true
}

现在在片段中，如果您显示向上箭头

activity.supportActionBar?.setDisplayHomeAsUpEnabled(true)

单击它可以使您返回上一个活动。

科特林：

class MyActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        ...
        supportFragmentManager.addOnBackStackChangedListener { setupHomeAsUp() }
        setupHomeAsUp()
    }

    private fun setupHomeAsUp() {
        val shouldShow = 0 < supportFragmentManager.backStackEntryCount
        supportActionBar?.setDisplayHomeAsUpEnabled(shouldShow)
    }

    override fun onSupportNavigateUp(): Boolean = 
        supportFragmentManager.popBackStack().run { true }

    ...
}

这是一个非常好的且可靠的解决方案：http : //vinsol.com/blog/2014/10/01/handling-back-button-press-inside-fragments/

这个家伙制作了一个抽象片段，用于处理backPress行为，并使用策略模式在活动片段之间切换。

对于你们中的某些人来说，抽象类可能会有一些缺点。

不久，链接的解决方案如下所示：

// Abstract Fragment handling the back presses

public abstract class BackHandledFragment extends Fragment {
    protected BackHandlerInterface backHandlerInterface;
    public abstract String getTagText();
    public abstract boolean onBackPressed();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if(!(getActivity()  instanceof BackHandlerInterface)) {
            throw new ClassCastException("Hosting activity must implement BackHandlerInterface");
        } else {
            backHandlerInterface = (BackHandlerInterface) getActivity();
        }
    }

    @Override
    public void onStart() {
        super.onStart();

        // Mark this fragment as the selected Fragment.
        backHandlerInterface.setSelectedFragment(this);
    }

    public interface BackHandlerInterface {
        public void setSelectedFragment(BackHandledFragment backHandledFragment);
    }
}   

活动中的用法：

// BASIC ACTIVITY CODE THAT LETS ITS FRAGMENT UTILIZE onBackPress EVENTS 
// IN AN ADAPTIVE AND ORGANIZED PATTERN USING BackHandledFragment

public class TheActivity extends FragmentActivity implements BackHandlerInterface {
    private BackHandledFragment selectedFragment;

    @Override
    public void onBackPressed() {
        if(selectedFragment == null || !selectedFragment.onBackPressed()) {
            // Selected fragment did not consume the back press event.
            super.onBackPressed();
        }
    }

    @Override
    public void setSelectedFragment(BackHandledFragment selectedFragment) {
        this.selectedFragment = selectedFragment;
    }
}