actionbar up navigation with fragments

2019-06-18 15:47发布

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我有三个选项卡的标签动作条/ viewpager布局说A，B和C。在标签c标签（片段），我加入另一片段说片段d。同

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

我修改动作条在DFragment的的onResume加起来按钮：

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

现在DFragment，当我按下硬件（手机）后退按钮，我回到与CFragment原来的选项卡式（ABC）的布局选择。我怎样才能实现与动作条上按钮此功能？

Answer 1:

实施OnBackStackChangedListener这个代码添加到您的片段活动。

@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;
}

Answer 2:

我知道了。只是重写onOptionsItemSelected在举办活动和弹出堆栈中，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;
    default:
        return super.onOptionsItemSelected(item);;
    }
}

呼叫getActionBar().setDisplayHomeAsUpEnabled(boolean); 和getActionBar().setHomeButtonEnabled(boolean); 在onBackStackChanged()如下面的答案说明。

Answer 3:

如果你有一个父活动，并希望这件事按钮，后退按钮的工作，您可以使用此代码：

这在主活动类添加到的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);
            }
        }

    });

然后添加onOptionsItemSelected像这样：

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

我一般用这一切的时候，似乎很合法

Answer 4:

你可以回去与像后退按钮按钮;

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

Answer 5:

我知道这个问题是旧的，但可能是有人（像我）也需要它。

如果你的活动延伸AppCompatActivity，你可以用一个简单的（两步）解决方案：

1 - 无论何时添加非家庭片段只显示向上按钮，commiting片段交易之后。像这样：

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

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

2 - 然后，当按了按钮，隐藏它。

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

而已。

Answer 6:

我用的组合罗杰·加尔松涅托的和sohailaziz的答案。我的应用程序有一个单一的MainActivity，和片段被加载到它的A，B，C。我的“家”片段（A）实现OnBackStackChangedListener，并检查返回堆栈的大小; 如果是小于1，那么它隐藏UP键。片段B和C总是加载后退按钮（在我的设计，B从A推出，和C向B发射）。在MainActivity本身只是对持久性有机污染物UP按钮自来水返回堆栈，并且有方法来显示/隐藏按钮，该片段致电：

MainActivity：

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();
    }
}

fragmentB，fragmentC：

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

    // other fragment init stuff
    ...
}

Answer 7:

这为我工作。覆盖onSupportNavigateUp和onBackPressed，例如（在科特林代码）;

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，在该片段中，如果显示的向上箭头

activity.supportActionBar?.setDisplayHomeAsUpEnabled(true)

点击它带你回到以前的活动。

Answer 8:

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 }

    ...
}

Answer 9:

这是一个很好的和可靠的解决方案： http://vinsol.com/blog/2014/10/01/handling-back-button-press-inside-fragments/

的人取得了处理该backPress行为，并使用该策略图案活性片段之间进行切换的抽象片段。

对于一些你有可能在抽象类有点缺点......

不久，从链接的解决方案是这样的：

// 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);
    }
}

在活动和使用情况：

// 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;
    }
}

文章来源: actionbar up navigation with fragments