java - 如何将 onSaveInstance 方法与 Recyclerview 一起使用

Question

我有一个应用程序，当屏幕旋转时，它应该将所有显示的数据保留到回收器中。回收器从自定义数组列表接收数据。还有第二个变量用于设置适配器内 VideoView 的 Uri。

已经尝试过 onSave 和 onRestoreIntance。也许我用错了它们。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    // Variables-----------------------------------------

     recyclerView = findViewById(R.id.recyclerView);
    Button video = findViewById(R.id.video);
    Button camera = findViewById(R.id.camera);
    Button send = findViewById(R.id.send);
    final EditText editText = findViewById(R.id.editText);


    // Layout Manager------------------------------------------------

    linearLayoutManager = new LinearLayoutManager(MainActivity.this);
    linearLayoutManager.setStackFromEnd(true);
    RecyclerView.ItemAnimator itemAnimator = new DefaultItemAnimator();
    recyclerView.setLayoutManager(linearLayoutManager);
    recyclerView.setItemAnimator(itemAnimator);


    // Adapter-----------------------------------------

        //adapter.notifyDataSetChanged();
        adapter =  new myAdapter(dati, this);
        recyclerView.setAdapter(adapter);



    // Click Listener Video button---------------------------------------- 
    video.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);
            startActivityForResult(intent,0);
        }
    });

    // Click Listener Camera button--------------------------------------
    camera.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
            startActivityForResult(intent,1);
        }
    });

    // Click Listener Send button-----------------------------------------
    send.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String string = editText.getText().toString();
            dati.add(new ModelloDati(0,string));
            adapter.notifyItemInserted(dati.size());
            editText.getText().clear();
            recyclerView.smoothScrollToPosition(dati.size());
            closeKeyboard();
        }
    });

    if(savedInstanceState != null)



linearLayoutManager.onRestoreInstanceState(
savedInstanceState.getParcelable("STATO_LISTA"));

}


@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable  
Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    switch (requestCode){
        case 0:
            try {
                Uri contentURI = data.getData();
                passUri = contentURI;
                String recordedVideoPath = getPath(contentURI);
                saveVideoToInternalStorage(recordedVideoPath);
                dati.add(new ModelloDati(2, contentURI));
                adapter.notifyItemInserted(dati.size());
                recyclerView.smoothScrollToPosition(dati.size());

            }catch (Throwable o){Log.i("CAM","User aborted action");}
        case 1:
            try {
                Bitmap bitmap = (Bitmap)data.getExtras().get("data");
                dati.add(new ModelloDati(1,bitmap));
                adapter.notifyItemInserted(dati.size());
                recyclerView.smoothScrollToPosition(dati.size());


            }catch(Throwable o){
                Log.i("CAM","User aborted action");
            }

    }


}


@Override
protected void onResume() {
    super.onResume();

    if (saveList != null) {
        linearLayoutManager.onRestoreInstanceState(saveList);
    }
}


@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    saveList = linearLayoutManager.onSaveInstanceState();
    outState.putParcelable("STATO_LISTA",saveList);
}


@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    if(savedInstanceState != null)
       savedInstanceState.getParcelable("STATO_LISTA");
}

}

Answer 1

Android 优惠 Architecture components这可以帮助您处理此类情况。例如ViewModel

The Android framework manages the lifecycles of UI controllers, such as activities and fragments. The framework may decide to destroy or re-create a UI controller in response to certain user actions or device events that are completely out of your control.

If the system destroys or re-creates a UI controller, any transient UI-related data you store in them is lost. For example, your app may include a list of users in one of its activities. When the activity is re-created for a configuration change, the new activity has to re-fetch the list of users. For simple data, the activity can use the onSaveInstanceState() method and restore its data from the bundle in onCreate(), but this approach is only suitable for small amounts of data that can be serialized then deserialized, not for potentially large amounts of data like a list of users or bitmaps.

所以基本上，您可以在 ViewModel 中保存适配器的数据集，并在 onCreate 中获取数据并将其设置到您的适配器中。

MyViewModel model = ViewModelProviders.of(this).get(MyViewModel.class);
new adapter(model.getData(),this); // just for the example.