android - 在 View 中动态添加 fragment

Question

我已经开始使用这个 How do I add a Fragment to an Activity with a programmatically created content view

在 Activity 中创建和添加 Fragment。

但是当我尝试在动态 View 中添加相同的 fragment 时，它失败了。

你能解决它背后的问题吗？

public class MainActivity extends FragmentActivity {

    private static final int CONTENT_VIEW_ID = 10101010;
    private static final int CONTENT_VIEW_ID1 = 10101011;

    public FragmentManager fm = getSupportFragmentManager();

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

        View view = new View(this);

        FrameLayout frame = new FrameLayout(this);
        frame.setId(CONTENT_VIEW_ID);
        frame.addView(view,new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
        view.setId(CONTENT_VIEW_ID1);
        setContentView(frame);
        if (savedInstanceState == null) {
            Fragment newFragment1 = new DebugExampleTwoFragment();
            FragmentTransaction ft = fm.beginTransaction(); 
            ft.add(CONTENT_VIEW_ID1, newFragment1);
            ft.commit();
        }

public static class DebugExampleTwoFragment extends Fragment {
        public static int count = 0;

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View v = new View(getActivity());
            v.setBackgroundColor(Color.RED);
            return v;
        }
    }

它因 ClassCastException 而失败，未显示确切的行号。

Answer 1

您可能会收到这样的消息:

java.lang.ClassCastException: android.view.View cannot be cast to android.view.ViewGroup

那是因为可以将 fragment 插入到 ViewGroup 或从 ViewGroup 继承的东西中。您不能将 fragment 插入到 View 中。要使您的代码运行，请更改此行:

View view = new View(this);

例如，这个:

FrameLayout view = new FrameLayout(this);//FrameLayout inherits from ViewGroup