处理每个片段的反压

Question

我在 Whosebug 上浏览了很多，并为我的项目做了一组最好的交易，但在处理 backpressed 时遇到问题。

这是我的基地activity class:

public class BaseAppCompatActivity extends LifecycleActivity {
    protected IBackPressedListener onBackPressedListener;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }


    protected FragmentTransaction getFragmentTransaction() {
        return getSupportFragmentManager().beginTransaction();
    }

    protected void addFragment(int fragmentContainer, Fragment fragment, String fragName, boolean addToBackStack) {
        FragmentTransaction ft = getFragmentTransaction();
        ft.add(fragmentContainer, fragment);
        if (addToBackStack)
            ft.addToBackStack(fragName);
        // Complete the changes added above
        ft.commitAllowingStateLoss();
    }

    public void setOnBackPressedListener(IBackPressedListener onBackPressedListener) {
        this.onBackPressedListener = onBackPressedListener;
    }

    @Override
    public void onBackPressed() {

    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        onBackPressedListener = null;
    }
}

这是我的 activity 类，我在其中添加片段并处理后压事件：

public class RechargeFragmentActivity extends BaseAppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recharge_fragment);

        /*Replace fragment*/
        addFragment(R.id.fragmentFrame, new SelectRechargeOperatorFragment(), AppFragments.FRAG_SELECT_RECHARGE_OPERATORS, true);
    }

    @Override
    public void onBackPressed() {
        if (getSupportFragmentManager().getBackStackEntryCount() > 1 && onBackPressedListener != null) {
            onBackPressedListener.onBackPressed();
        } else
            finish();
    }

}

现在我在片段中实现了 Onbackpressed 侦听器，它对一个反压效果很好，之后它只拾取最后一个被弹出的片段的实例。

public class SelectRechargeOperatorFragment extends BaseFragment {
    @Inject
    public SelectRechargeOperatorLiveDataModel operatorLiveDataModel;
    @BindView(R.id.rv_select_operator)
    RecyclerView rvSelectOperators;
    @BindView(R.id.proceedLayout)
    RelativeLayout btnProceed;
    private RechargeOperatorsAdapter adapter;


    public SelectRechargeOperatorFragment() {
        //empty constructor required
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ((BaseAppCompatActivity) fragmentContext).setOnBackPressedListener(this);
    }

    @Override
    protected void onInject(GraphComponent applicationComponent) {
        super.onInject(applicationComponent);
        applicationComponent.inject(this);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View convertView = inflater.inflate(R.layout.fragment_select_recharge_operator, container, false);
        ButterKnife.bind(this, convertView);

        /*fetch-views*/
        setUpOperatorRecyclerView();
        proceedToRecharge();

        return convertView;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public void onResume() {
        super.onResume();
    }

    private void proceedToRecharge() {
        btnProceed.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                addFragment(R.id.fragmentFrame, new RechargeAirtimeFargment(), AppFragments.FRAG_RECHARGE_AIRTIME_PLANS, true);
            }
        });
    }
 @Override
    public void onBackPressed() {
        super.onBackPressed();
        getActivity().getSupportFragmentManager().popBackStack();
    }


}

这在我只添加一个片段时效果很好。当我添加多个片段时，它仅适用于第一次弹出片段，然后它 returns 我是旧片段 onBackpressed 侦听器。为什么？

Answer 1

问题是，每次添加片段时，activity 中的 onBackPressedListener 都会被新对象覆盖。所以在弹出最后一个片段之后逻辑失败了。请尝试以下操作。

从您的 Activity

setOnBackPressedListener

onBackPressedListener

在您的片段中实施 IBackPressedListener。也许您可以使用 basefragment 来避免代码重复。根据您的需要选择。

将 activity 中的 onBackPressed 更改为

 @Override
 public void onBackPressed() {
        if (getSupportFragmentManager().getBackStackEntryCount() > 1) {
            Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.fragmentFrame);
           if(null != currentFragment && currentFragment instance of IBackPressedListener) {
               ((IBackPressedListener)currentFragment).onBackPressed();
           }
        } else
            finish();
    }

处理每个片段的反压

Handling backpressed on each fragment

android

android-fragments

onbackpressed