java - 在方向改变时查看相同的缩略图

Question

我试图在方向更改后在此处获取位图图片以显示在 ImageView 中，而不是从可绘制文件夹中获取的图片。我知道savedInstance可以做到这一点，但不确定如何使用它。我也尝试过 onCofigureationChange()，但没有运气。

public class MainActivity extends AppCompatActivity {

static final int REQUEST_IMAGE_CAPTURE = 1;

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

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {

    ImageView imageView = (ImageView)findViewById(R.id.imageView);

    if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
        Bundle extras = data.getExtras();
        Bitmap imageBitmap = (Bitmap) extras.get("data");
        imageView.setImageBitmap(imageBitmap);
    }
}

public void taBilde(View view) {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
        startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
    }
}
}

Answer 1

要保留生命周期更改中的数据，您可以使用 this link 中的 ViewModel .

更新

我用 kotlin 编写了这个解决方案的代码。你可以用java编写它。

import android.arch.lifecycle.LiveData
import android.arch.lifecycle.MutableLiveData
import android.arch.lifecycle.ViewModel
import android.graphics.Bitmap


/**
 * Created by Amin on 9/6/2018.
 */
class ThumbnailHolderViewModel : ViewModel() {

    private var thumbnail: MutableLiveData<Bitmap>? = null

    fun setThumbnail(bitmap: Bitmap) {
        if (thumbnail == null) {
            thumbnail = MutableLiveData()
        }
        thumbnail?.value = bitmap
    }

    fun getThumbnail(): LiveData<Bitmap>? {
        return thumbnail
    }

}

在您的 Activity 中初始化 ViewModel:

val viewModel = ViewModelProviders.of(this).get(ThumbnailHolderViewModel::class.java)
viewModel.setThumbnail(yourThumbnailBitmap)

并从中获取保留的数据:

val viewModel = ViewModelProviders.of(this).get(ThumbnailHolderViewModel::class.java)
viewModel.getThumbnail()?.observe(this, Observer<Bitmap?> { bitmap ->
    if (bitmap != null) {
        // do sth...
    }
})