如何在适配器中获得WRITE_EXTERNAL_STORAGE权限?

Question

我想从远程url下载图像，我需要获得用户权限来保存图像，但我无法在GridAdapter.java文件中做到这一点，这在适配器中不起作用:

requestPermissions((Activity) context,new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE},DOWNLOAD_REQUEST_CODE);

我已经尝试了很多方法，这些方法都可以在网上找到，但似乎没有工作，

likeActivityCompat.requestPermissions(context,new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE},DOWNLOAD_REQUEST_CODE);

requestPermissions((Activity) context.getApplicationContext(),new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE},DOWNLOAD_REQUEST_CODE);

Answer 1

在GridActivity类中创建一个接口并在GridAdapter类中实现

interface IPermissionCallback{
void askForStoragePermission();
Boolean checkSelfStoragePermission();
}
public class GridActivity extends AppCompatActivity implements 
IPermissionCallback {
private static final int DOWNLOAD_REQUEST_CODE = 1001;
private GridAdapter adapter;
@Override
public void onCreate(@Nullable Bundle savedInstanceState, @Nullable 
PersistableBundle persistentState) {
super.onCreate(savedInstanceState, persistentState);

//other codes...
//initialize GridAdapter here and then call setPermissionCallback() 
//method as shown below
adapter.setPermissionCallback(this);
}

@Override
public void askForStoragePermission() {
requestPermissions(new String[] 
{android.Manifest.permission.WRITE_EXTERNAL_STORAGE},
DOWNLOAD_REQUEST_CODE);
}
@Override
public Boolean checkSelfStoragePermission() {

if(checkCallingOrSelfPermission(
android.Manifest.permission.WRITE_EXTERNAL_STORAGE) == 
PackageManager.PERMISSION_GRANTED){
return true;
}
return false;
}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] 
permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, 
grantResults);
if (requestCode == DOWNLOAD_REQUEST_CODE 
&& grantResults[0] == PackageManager.PERMISSION_GRANTED){
//permission granted update GridAdapter to do next task
adapter.onPermissionResult(true);
}else{
//permission denied update GridAdapter to do next task
adapter.onPermissionResult(false);
}
}
}

在Grid Adapter中你需要写这些方法

public class GridAdapter/**extends needed classes etc.*/{
private IPermissionCallback callback;

public void yourMethodWhereYouDownloadingImg(){
if (callback != null && callback.checkSelfStoragePermission()){
//already permission is granted
}else{
callback.askForStoragePermission();
}
}
public void setPermissionCallback(IPermissionCallback c){
this.callback = c;
}
public void onPermissionResult(Boolean permissionGranted){
/**
* if @permissionGranted is true download image else inform user 
that permission is denied
*/
}
}