Android-更改 fragment 时将 ImageView 中的图像保留在 fragment 上

Question

我有下面的代码。我将 fragment 中图库中的图像设置为 ImageView。问题是当我更改 fragment 并再次返回到带有 ImageView 的 fragment 时，它具有默认图像，而不是我设置的图像。

public class Fragment_user extends Fragment {

 private static final int SELECT_PICTURE = 1;
 private String selectedImagePath=null;
 private ImageView img;

@Override
public View onCreateView(
        LayoutInflater inflater,
        ViewGroup container,
        Bundle savedInstanceState){
    View rootView = inflater.inflate(R.layout.fragment_user, container, false);
    //if (savedInstanceState == null){
        img = (ImageView)rootView.findViewById(R.id.userImage);
    //}else{
        //Bitmap bitmap = (Bitmap) savedInstanceState.getParcelable("bitmap");
        //img.setImageBitmap(bitmap);
    //}


            img.setOnClickListener(new OnClickListener() {
                public void onClick(View arg0) {
                    Intent intent = new Intent();
                    intent.setType("image/*");
                    intent.setAction(Intent.ACTION_GET_CONTENT);
                    startActivityForResult(Intent.createChooser(intent,"Select Picture"), SELECT_PICTURE);
                }
            });     
    return rootView;
}
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (resultCode == MainActivity.RESULT_OK) {
        if (requestCode == SELECT_PICTURE) {
            Uri selectedImageUri = data.getData();
            selectedImagePath = getPath(selectedImageUri);
            System.out.println("Image Path : " + selectedImagePath);
            img.setImageURI(selectedImageUri);
        }
    }
}

public String getPath(Uri uri) 
{
    String[] projection = { MediaStore.Images.Media.DATA };
    Cursor cursor = getActivity().getContentResolver().query(uri, projection, null, null, null);
    if (cursor == null) return null;
    int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
    cursor.moveToFirst();
    String s=cursor.getString(column_index);
    cursor.close();
    return s;
}

@Override
public void onSaveInstanceState(Bundle outState) {        
    super.onSaveInstanceState(outState);
    // Save the image bitmap into outState
    Bitmap bitmap = ((BitmapDrawable)img.getDrawable()).getBitmap();
    outState.putParcelable("bitmap", bitmap);
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    // Read the bitmap from the savedInstanceState and set it to the ImageView
    if (savedInstanceState != null){
        Bitmap bitmap = (Bitmap) savedInstanceState.getParcelable("bitmap");
        img.setImageBitmap(bitmap);
     }  
}

}

我有 onSaveInstanceState 方法将所选图像保存到位图，并使用 onActivityCreated 方法在我返回 Fragment 时将图像设置回 ImageView。但这是行不通的。有什么帮助吗？ 提前致谢

Answer 1

发生这种情况是因为您的 fragment 根据 Fragments Lifecycle 失去了 View 。为了解决您的问题，请采取以下行动:

1. 创建全局变量private Uri mSelectedImageUri;

2. 使用此变量代替本地 Uri selectedImageUri:

   if (requestCode == SELECT_PICTURE) {
       mSelectedImageUri = data.getData();
       selectedImagePath = getPath(mSelectedImageUri);
       System.out.println("Image Path : " + selectedImagePath);
       img.setImageURI(mSelectedImageUri);
   }
   

3. 在此行下方添加检查img = (ImageView)rootView.findViewById(R.id.userImage);:

   if (mSelectedImageUri != null) {
       img.setImageURI(mSelectedImageUri);
   }