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android - 将 Circleimageview 的状态保存在片段内

问题描述

我有一个带有 circleimageview 的片段，用作稍后正确保存在数据库中的个人资料图像。我的问题是使用 onSaveInstanceState 和 onPause/onStop 保存 imageview 的状态，以在将它们保存到数据库之前以及在执行屏幕旋转之后保持它们的状态。这是我的代码

public class MyFragment extends Fragment implements View.OnClickListener {
    private CircleImageView mPhoto;
    private byte[] bytes = null;
    private Bitmap photo = null;

    @Override
    public void onSaveInstanceState(@NonNull Bundle outState) {
        super.onSaveInstanceState(outState);
        if(bytes!=null) {
            outState.putByteArray("bytes", bytes);
        }
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        LayoutInflater lf = getActivity().getLayoutInflater();
        view =  lf.inflate(R.layout.my_fragment,container,false);
        mPhoto = (CircleImageView) view.findViewById(R.id.photo);

        view.findViewById(R.id.photo).setOnClickListener(this);

        if(savedInstanceState!=null){
            if(savedInstanceState.containsKey("bytes")){
                bytes = savedInstanceState.getByteArray("bytes");
                if(bytes != null) {
                    //but with a screen rotation the image is not restored
                    photo = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
                    mPhoto.setImageBitmap(photo);
                }
            }
        }
        return view;
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.photo:
                Intent i = new Intent(Intent.ACTION_PICK,android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                try {
                    startActivityForResult(Intent.createChooser(i, "Select Picture"), 0);
                }catch (ActivityNotFoundException ex){
                    ex.printStackTrace();
                }
                break;
        }

    }
    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode==0 && resultCode == Activity.RESULT_OK) {
            Uri path = data.getData();
            Bitmap tmp = null;
            try {
                tmp = MediaStore.Images.Media.getBitmap(getContext().getContentResolver(), path);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if(tmp != null) {
                mPhoto.setImageBitmap(photo);
                bytes = getBitmapAsByteArray(photo);
                //tested, bytes is not null and the photo are restored correctly when saved on the database 
            }

        }
    }
    @Override
    public void onResume() {
        super.onResume();
        bytes = getActivity().getIntent().getByteArrayExtra("bytes");
        if(bytes != null) {
            //here bytes is null
            photo = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
            mPhoto.setImageBitmap(photo);
        }

    }


    @Override
    public void onStop() {
        super.onStop();
        if(bytes!=null)
            getActivity().getIntent().putExtra("bytes",bytes);
    }
}

这样在屏幕旋转过程中图像不保持不变，如何正确实现onsavedInstanceState、onStop和onResume？

标签： androidimageviewonresumeonsaveinstancestate

解决方案

最简单的方法将 ViewModel 与您的片段一起使用。

参考：https ://developer.android.com/topic/libraries/architecture/viewmodel.html

更新：

Step1：在build.gradle中添加View Model依赖

def lifecycle_version = "2.0.0"
implementation "androidx.lifecycle:lifecycle viewmodel:$lifecycle_version"

第 2 步：为 Fragment 创建 ViewModel

public class MyFragmentViewModel extends ViewModel {
}

第三步：在 MyFragment 中设置 ViewModel

public class MyFragment extends Fragment {
 public void onStart() {
     MyFragmentViewModel userModel = ViewModelProviders.of(getActivity()).get(MyFragmentViewModel.class);
 }
}

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