活动被破坏后ImageView丢失图像
我正在尝试创建一个应用程序,让用户可以选择要在其个人资料中显示的图片。我可以在imageview上浏览和设置他们选定的图像。但是一旦活动被破坏,图像就会丢失。我试图实现onSaveInstanceState,但它仍然是一样的。我想知道我是否正确使用它。我希望你能帮助像我这样的新手。提前致谢。下面是我使用的代码:活动被破坏后ImageView丢失图像
public class AccountFragment extends Fragment implements OnClickListener {
private LoginDataBaseAdapter loginDataBaseAdapter;
Bitmap image;
Bitmap bitmap;
String picture_location;
TextView textTargetUri;
ImageView targetImage;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_account, container, false);
textTargetUri = (TextView) rootView.findViewById(R.id.targeturi);
targetImage=(ImageView) rootView.findViewById(R.id.profpic);
targetImage.setOnClickListener(new ImageView.OnClickListener(){
@Override
public void onClick(View arg0) {
Intent intent = new Intent(Intent.ACTION_PICK,
android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(intent, 0);
}});
if (savedInstanceState != null) {
//if there is a bundle, use the saved image resource (if one is there)
image = savedInstanceState.getParcelable("BitmapImage");
targetImage.setImageBitmap(image);
textTargetUri.setText(savedInstanceState.getString("path_to_picture"));
}
return rootView;
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState){
super.onSaveInstanceState(savedInstanceState);
savedInstanceState.putParcelable("BitmapImage", bitmap);
savedInstanceState.putString("path_to_picture", picture_location);
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == Activity.RESULT_OK){
Uri targetUri = data.getData();
picture_location = targetUri.toString();
textTargetUri.setText(targetUri.toString());
Bitmap bitmap;
try {
bitmap = BitmapFactory.decodeStream(getActivity().getContentResolver().openInputStream(targetUri));
targetImage.setImageBitmap(bitmap);
}
catch (FileNotFoundException e){
e.printStackTrace();
}
}
}
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
}}
顺便说一句,你可能已经注意到,而不是在OnCreate后使用onRestoreInstanceState,我试图用不同的方法。我从另一个问题找到了一个答案,你也可以在oncreate中实现它。我使用它,因为每当我声明函数onRestoreInstanceState我被要求删除@Override注释。
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState){
image = savedInstanceState.getParcelable("BitmapImage");
targetImage.setImageBitmap(image);
textTargetUri.setText(savedInstanceState.getString("path_to_picture"));
}
使用onSaveInstanceState和onCreate/onRestoreInstanceState用于短期活动状态保存 - 但不用于持久存储应用程序的数据。
你可以阅读有关的onSaveInstanceState here
你可以阅读有关持久性存储here
codeMagic使用SharedPrefs(见持久存储链接)为您的长期持久性存储建议。如果你想这样做,我会建议在你的onActivityResult方法中保存图像URI(链接有一个很好的例子),然后调用一个方法来读取SharedPref并加载你可以调用的图像onCreate以及onActivityResult。
您可能还希望将自己的图像/位图副本存储在应用程序自己的内部存储器中(请参阅持久存储链接)。
如果你没有完成的活动,您可以使用onSavedInstance()
存储picture_location
值,并将其绑定回无论是从picture_location
值onCreate(SavedInst)
/onRestore()
。
如果位图实例状态不是建议的方式来保存所选图像的信息。
您可以在这里找到的解释:Handling configuration Changes
我广泛地在这里的博客上讲述它:Retain selected Image during Screen Rotation
下面我贴我的实现图示的解决方案:
1 - 创建一个片段,并对其进行配置保留在内存中
import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.v4.app.Fragment;
public class ImageRetainingFragment extends Fragment {
private Bitmap selectedImage;
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// retain this fragment
setRetainInstance(true);
}
public void setImage(Bitmap selectedImage) {
this.selectedImage = selectedImage;
}
public Bitmap getImage() {
return this.selectedImage;
}
}
2 - 在您的活动中使用它
private static final String FRAGMENT_NAME = "imageFragment";
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
....
initializeImageRetainingFragment();
tryLoadImage();
}
private void initializeImageRetainingFragment() {
// find the retained fragment on activity restarts
FragmentManager fragmentManager = getSupportFragmentManager();
this.imageRetainingFragment = (ImageRetainingFragment) fragmentManager.findFragmentByTag(FRAGMENT_NAME);
// create the fragment and bitmap the first time
if (this.imageRetainingFragment == null) {
this.imageRetainingFragment = new ImageRetainingFragment();
fragmentManager.beginTransaction()
// Add a fragment to the activity state.
.add(this.imageRetainingFragment, FRAGMENT_NAME)
.commit();
}
}
private void tryLoadImage() {
if (this.imageRetainingFragment == null) {
return;
}
Bitmap selectedImage = this.imageRetainingFragment.getImage();
if (selectedImage == null) {
return;
}
ImageView selectedImageView = (ImageView)findViewById(R.id.selectedImage);
selectedImageView.setImageBitmap(selectedImage);
}
您是否想要在用户返回时保存图像? – 2014-08-29 14:26:56
如果你想保留图片,即使用户离开应用程序,那么你应该保存在'SharedPrefs'或DB的文件路径。 – codeMagic 2014-08-29 14:29:31