Question

我试图将MyData（Parcelable对象包括ArrayList）从AFragment传递给BFragment。

当然，它有效。但问题是，当我将数据（MyData）从AFragment传递给BFragment时，arraylist（mList）的引用是相同的。这会导致我在BFragment中更改mList的值时，AFragment中的mList值也会发生变化。我不知道解决这个问题。

我查看了有关Parcelable的各种文章，最后我发现Parcelable只在两个对象处于不同任务时重新创建实例。

如何使用新实例传递数据？

我写了如下代码。

迈德特：

public class MyData implements Parcelable {

public List<String> mList = new ArrayList<>(0);

@Override
public int describeContents() {
    return 0;
}

@Override
public void writeToParcel(Parcel out, int flags) {
    out.writeStringList(mList);
}

public static final Parcelable.Creator<MyData> CREATOR = new Parcelable.Creator<MyData>() {
    public MyData createFromParcel(Parcel in) {
        return new MyData(in);
    }

    public MyData[] newArray(int size) {
        return new MyData[size];
    }
};

private MyData(Parcel in) {
    in.writeStringList(mList);
}

public MyData() {
}
}

MainActivity ：

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    SampleFragment sampleFragment = new SampleFragment();
    replaceFragment(sampleFragment);
}

public void replaceFragment(Fragment fragment) {
    FragmentManager manager = getSupportFragmentManager();

    if (manager.findFragmentByTag(fragment.getClass().getCanonicalName()) != null) {
        return;
    }
    FragmentTransaction transaction = manager.beginTransaction();
    transaction.replace(R.id.container_layout, fragment, fragment.getClass().getCanonicalName());
    transaction.addToBackStack(null);
    transaction.commit();
}
}

AFragment ：

public class SampleFragment extends Fragment implements View.OnClickListener {

MainActivity mActivity;

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    mActivity = (MainActivity) context;
}

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

@Nullable
@Override
public View onCreateView(final LayoutInflater inflater, @Nullable final ViewGroup container, @Nullable final Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.sample1, container, false);
    view.findViewById(R.id.button).setOnClickListener(this);
    return view;
}

@Override
public void onClick(View v) {
    int id = v.getId();
    if (id == R.id.button) {
        List<String> list = new ArrayList<>(0);
        list.add("sample1");
        list.add("sample2");
        list.add("sample3");
        HogeData data = new HogeData();
        data.mList = list;
        SampleFragment2 sampleFragment2 = new SampleFragment2();
        Bundle bundle = new Bundle();
        bundle.putParcelable(sampleFragment2.getClass().getCanonicalName(), data);
        sampleFragment2.setArguments(bundle);
        mActivity.replaceFragment(sampleFragment2);
    }
}
}

BFragment ：

public class SampleFragment2 extends Fragment {

MainActivity mActivity;
HogeData mData;

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    mActivity = (MainActivity) context;
}

@Override
public void onCreate(@Nullable final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Bundle bundle = getArguments();
    mData = bundle.getParcelable(getClass().getCanonicalName());
}

@Nullable
@Override
public View onCreateView(final LayoutInflater inflater, @Nullable final ViewGroup container, @Nullable final Bundle savedInstanceState) {
    return inflater.inflate(R.layout.sample2, container, false);
}

在值不是引用

0 个答案: