我们创建了一个小的库来处理多个片段和/或活动中的背压。使用就像在gradle文件中添加依赖一样简单:

compile 'net.skoumal.fragmentback:fragment-back:0.1.0'

让你的片段实现BackFragment接口:

public abstract class MyFragment extends Fragment implements BackFragment {

    public boolean onBackPressed() {

        // -- your code --

        // return true if you want to consume back-pressed event
        return false;
    }

    public int getBackPriority() {
        return NORMAL_BACK_PRIORITY;
    }
}

通知你的片段关于背压:

public class MainActivity extends AppCompatActivity {

    @Override
    public void onBackPressed() {
        // first ask your fragments to handle back-pressed event
        if(!BackFragmentHelper.fireOnBackPressedEvent(this)) {
            // lets do the default back action if fragments don't consume it
            super.onBackPressed();
        }
    }
}

欲了解更多详细信息和其他用例，请访问GitHub页面:

https://github.com/skoumalcz/fragment-back

当你在Fragments之间转换时，调用addToBackStack()作为FragmentTransaction的一部分:

FragmentTransaction tx = fragmentManager.beginTransation();
tx.replace( R.id.fragment, new MyFragment() ).addToBackStack( "tag" ).commit();

如果你需要更详细的控制(例如，当一些片段可见时，你想要抑制返回键)，你可以在你的片段的父视图上设置一个OnKeyListener:

//You need to add the following line for this solution to work; thanks skayred
fragment.getView().setFocusableInTouchMode(true);
fragment.getView().requestFocus();
fragment.getView().setOnKeyListener( new OnKeyListener()
{
    @Override
    public boolean onKey( View v, int keyCode, KeyEvent event )
    {
        if( keyCode == KeyEvent.KEYCODE_BACK )
        {
            return true;
        }
        return false;
    }
} );

我宁愿这样做:

private final static String TAG_FRAGMENT = "TAG_FRAGMENT";

private void showFragment() {
    final Myfragment fragment = new MyFragment();
    final FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
    transaction.replace(R.id.fragment, fragment, TAG_FRAGMENT);
    transaction.addToBackStack(null);
    transaction.commit();
}

@Override
public void onBackPressed() {
    final Myfragment fragment = (Myfragment) getSupportFragmentManager().findFragmentByTag(TAG_FRAGMENT);

    if (fragment.allowBackPressed()) { // and then you define a method allowBackPressed with the logic to allow back pressed or not
        super.onBackPressed();
    }
}

在你的oncreateView()方法中，你需要写这些代码，在KEYCODE_BACk条件下，你可以写任何你想要的功能

View v = inflater.inflate(R.layout.xyz, container, false);
//Back pressed Logic for fragment 
v.setFocusableInTouchMode(true); 
v.requestFocus(); 
v.setOnKeyListener(new View.OnKeyListener() { 
    @Override 
    public boolean onKey(View v, int keyCode, KeyEvent event) {
        if (event.getAction() == KeyEvent.ACTION_DOWN) {
            if (keyCode == KeyEvent.KEYCODE_BACK) {
                getActivity().finish(); 
                Intent intent = new Intent(getActivity(), MainActivity.class);
                startActivity(intent);

                return true; 
            } 
        } 
        return false; 
    } 
}); 

我们创建了一个小的库来处理多个片段和/或活动中的背压。使用就像在gradle文件中添加依赖一样简单:

compile 'net.skoumal.fragmentback:fragment-back:0.1.0'

让你的片段实现BackFragment接口:

public abstract class MyFragment extends Fragment implements BackFragment {

    public boolean onBackPressed() {

        // -- your code --

        // return true if you want to consume back-pressed event
        return false;
    }

    public int getBackPriority() {
        return NORMAL_BACK_PRIORITY;
    }
}

通知你的片段关于背压:

public class MainActivity extends AppCompatActivity {

    @Override
    public void onBackPressed() {
        // first ask your fragments to handle back-pressed event
        if(!BackFragmentHelper.fireOnBackPressedEvent(this)) {
            // lets do the default back action if fragments don't consume it
            super.onBackPressed();
        }
    }
}

欲了解更多详细信息和其他用例，请访问GitHub页面:

https://github.com/skoumalcz/fragment-back

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

这家伙已经制作了一个抽象片段，处理backPress行为，并使用策略模式在活动片段之间切换。

对于你们中的一些人来说，抽象课程可能会有一些缺陷。

简单地说，链接中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);
    }
}   

和在活动中的用法:

// 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;
    }
}