android - 三个 Fragments，第二个 Fragments 的接口(interface)需要在 Main 和 Second Activity 上实现

Question

在 Eclipse 中采用默认的“Master/Detail”流程模板，并添加第三个 Fragment(我们称它为 Edit，从预先存在的 Detail Fragment 启动)，我现在希望在用户时打开 Edit Fragment单击详细信息 fragment 中的项目。

我已经在 Detail fragment 上实现了一个接口(interface)，但是根据应用程序是在 Tablet 还是 Phone(是否双面板)上，Iterface 需要由 Detail Activity 或 Main Activity 实现为了发挥作用。我认为这是由于当设备未处于双 Pane 模式时模板将详细 fragment 的打开作为 Activity 实现的方式。

我是否错误地实现了这一点，或者是否有最佳实践可以让我将接口(interface)的实现统一到主要 Activity 中？

这里是主 fragment 和细节 fragment 的一些简化 fragment ，显示了对细节 fragment 接口(interface)的双重实现的要求。

WaveListWactivity.java 的代码(第一个 fragment )

public class WaveListActivity extends FragmentActivity implements
        WaveListFragment.Callbacks,WaveDetailFragment.Callbacks {
    private boolean mTwoPane;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_wave_list);
        if (findViewById(R.id.wave_detail_container) != null) {
            mTwoPane = true;
            ((WaveListFragment) getSupportFragmentManager().findFragmentById(
                    R.id.wave_list)).setActivateOnItemClick(true);
        }
    }

    //Interface from WaveListFragment
    @Override
    public void onWaveSelected(int id) {
        if (mTwoPane) {
            getSupportFragmentManager().beginTransaction()
                    .replace(R.id.wave_detail_container, new WaveDetailFragment()).commit();

        } else {
            Intent detailIntent = new Intent(this, WaveDetailActivity.class);
            startActivity(detailIntent);
        }
    }

    //Interface from WaveDetailFragment
    @Override
    public void onItemSelected(int id) {
        if (mTwoPane) {
            getSupportFragmentManager().beginTransaction()
                    .replace(R.id.wave_detail_container, new WaveEditFragment()).addToBackStack(null).commit();

        } else {
            Intent detailIntent = new Intent(this, WaveDetailActivity.class);
            startActivity(detailIntent);
        }
    }
}

WaveDetailActivity.java 代码(第二个 fragment )

public class WaveDetailActivity extends FragmentActivity implements WaveDetailFragment.Callbacks {
    private boolean mTwoPane;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_wave_detail);
        if (findViewById(R.id.wave_detail_container) != null) {
            mTwoPane = true;
        }

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction().add(R.id.wave_detail_container, new WaveDetailFragment()).commit();
        }
    }

    //Callback from WaveDetailFragment
    @Override
    public void onItemSelected(int id) {
        if (mTwoPane) {
            getSupportFragmentManager().beginTransaction().replace(R.id.wave_detail_container, new WaveEditFragment()).addToBackStack(null).commit();

        } else {
            Intent detailIntent = new Intent(this, WaveEditActivity.class);
            startActivity(detailIntent);
        }
    }
}

Answer 1

我认为您可能对 FragmentActivity、Fragments 和您需要在 Activity 上实现的回调接口(interface)之间的区别感到有些困惑>。从外观上看，所有代码 fragment 都是 Activity 类，不是 Fragments。我希望 Fragment 看起来像这样:

/** From http://developer.android.com/training/basics/fragments/communicating.html */

public class HeadlinesFragment extends ListFragment {
OnHeadlineSelectedListener mCallback;

// Container Activity must implement this interface
public interface OnHeadlineSelectedListener {
    public void onArticleSelected(int position);
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);

    // This makes sure that the container activity has implemented
    // the callback interface. If not, it throws an exception
    try {
        mCallback = (OnHeadlineSelectedListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement OnHeadlineSelectedListener");
    }
}

...
}

然后是您的Activity:

public static class MainActivity extends Activity
    implements HeadlinesFragment.OnHeadlineSelectedListener{
...

public void onArticleSelected(int position) {
    // The user selected the headline of an article from the HeadlinesFragment
    // Do something here to display that article
}
}

整体的“流程”应该是:

• fragment 充当 UI 代码块，带有所有有趣内容的回调。
• Activity 实现的回调。

您可以执行的操作总数取决于 fragment ，而 fragment 又取决于您的屏幕大小(因此您可能有 2 个 fragment ，它们会馈送到单个 Activity 中)。决定是否显示一个或两个 fragment 的逻辑应该在Activity中完成。