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Fragment笔记

生命周期

  • onAttach(Activity) 与一个Activity相关联,getActivity()
  • onCreate(Bundle)
  • onCreateView(Layoutinflater, ViewGroup, Bundle) 返回与Fragment相关的View
  • onActivityCreated(Bundle)
  • onViewStateResourced(Bundle) Fragment其View层次的所有保存状态都已恢复时触发
  • onStart() 触发同步Activity
  • onResume() 触发同步Activity
  • onPause() 触发同步
  • onStop() 触发同步
  • onDestroyView() 触发同步
  • onDestroy 触发同步
  • onDetach() 此时调用getActivity()返回空值,确保与Activity没有任何关联

给予Fragment数据

Fragment可以保存和恢复状态,需要一个默认的构造器;可以使一个Fragment与Activity相关联之前,通过静态newInstance()建立一个Fragment的自变量

示例:传递一个参数给fragment,并在创建View时使用

public class TextViewFragment extends Fragment {
    private static final String KEY_TEXY = "text";

    public static TextViewFragment newInstance(String text) {
        TextViewFragment f = new TextViewFragment();

        Budle args = new Bundle();
        args.putString(KEY_TEXT, text);
        f.setArguments(args);

        return f;
    }

    public String getText() {
        return getArguments().getString(KEY_TEXT);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstatanceState) {
        TextView tv = new TextView(getActivity());
        tv.setText(getText());
        return tv;
    }
}

通过调用setRetainInstance(true)方法可以在Activity重建时仍然保留Fragment,这样就不用onDestroy()onCreate()了。

与Activity通讯

示例:简单的DialogFragment

public class SampleDialogFragment extends DialogFragment {
    public interface OnDialogChoiceListener {
        public void onDialogCanceled();
        public void onDialogConfirmed();
    }

    private static final String ARG_CONTENT_RESOURCE_ID = "contentResourceId";
    private static final String ARG_CONFIRM_RESOURCE_ID = "confirmResourceId";

    private int mContentResourceId;
    private int mConfirmResourceId;

    private onDialogChoiceListener mListener;

    public static SampleDialogFragment newInstance(int contentResourceId, int confirmResourceId) {
        SampleDialogFragment dialog = new SampleDialogFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_CONTENT_RESOURCE_ID, contentResourceId);
        args.putInt(ARG_CONFIRM_RESOURCE_ID, confirmResourceId);
        fragment.setArguments(args);
        return dialog;
    }

    public SampleDialogFragment {
        // 必须是空的公共构造器
    }

    @Override
    public void static onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        final Bundle args = getArguments();
        if (args == null) {
            throw new IlleagalStateException("No arguments set, use the "
                + " newInstance method to construct this fragment");
        }
        mContentResourceId = args.getInt(ARG_CONTENT_RESOURCE_ID);
        mConfirmResourceId = args.getInt(ARG_CONFIRM_RESOURCE_ID);
    }

    @NonNull
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage(mContentResourceId);
            .setPositiveButton(mConfirmResourceId, new DialogInterface.OnClickListener() {
                public void OnClick(DialogInterface dialog, int id) {
                    mListener.onDialogConfirmed();
                }
            })
            .setNavigationButton(R.string.cancel, new DialogInterface.OnClickListener() {
                public void OnClick(DialogInterface dialog, int id) {
                    mListener.onDialogCanceled();
                }
            })
        return builder.create();
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttch(activity);
        try {
            mListener = (OnDialogChoiceListener) activity;
        } catch (ClassException e) {
            throw new ClassCastException(activity.toString(), " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }
}

执行Fragment事务

getSupportFragmentManager().beginTransaction()
    .add(R.id.container, ExampleFragment.newInstance())
    .addToBackStack(null)
    .commit();

最后更新: 2020年6月24日