如何在 android API 19 (KitKat) 中保持权限？

Question

在我的应用程序中，我将图像路径存储在我的 SQlite 数据库中以供进一步使用。我得到的路径是

content://com.android.providers.media.documents/document/image%3A71964

当我从数据库中检索此路径并尝试从 android 抛出的该路径中检索图像时

java.lang.SecurityException: Permission Denial: opening provider
com.android.providers.media.MediaDocumentsProvider 
from ProcessRecord{42c84ec8 23911:com.gots.gb/u0a248} (pid=23911, uid=10248) 
requires android.permission.MANAGE_DOCUMENTS or android.permission.MANAGE_DOCUMENTS

根据https://developer.android.com/guide/topics/providers/document-provider.html#permissions我需要通过添加以下代码来持久化权限

final int takeFlags = intent.getFlags()
        & (Intent.FLAG_GRANT_READ_URI_PERMISSION
        | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
// Check for the freshest data.
getContentResolver().takePersistableUriPermission(uri, takeFlags);

当我将此代码添加到扩展 BaseAdapter android 抛出的 ImageAdapter 类中时

08-21 02:14:38.530: W/System.err(24452): java.lang.SecurityException:
No permission grant found for UID 10248 and Uri 
content://com.android.providers.media.documents/document/image:71964

这是我的 ImageAdapter 代码的相关部分

public View getView(int position, View convertView, ViewGroup parent) {
    ImageView imageView ;


    if (convertView == null){
        imageView = new ImageView(mContext);
        imageView.setLayoutParams(new GridView.LayoutParams(185, 185));
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        imageView.setPadding(8, 8, 8, 8);

    }
    else{
        imageView = (ImageView)convertView ;
    }

    InputStream is = null;
    Bitmap bitmap = null ;

    try {

        Log.d(TAG,String.valueOf(list.get(position)));
        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        final int takeFlags = intent.getFlags()
                & (Intent.FLAG_GRANT_READ_URI_PERMISSION
                | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
        // Check for the freshest data.

        if (Build.VERSION.SDK_INT >= 19){
            mContext.getContentResolver().takePersistableUriPermission(list.get(position), takeFlags);
        }


        is = mContext.getContentResolver().openInputStream(list.get(position));

        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inSampleSize = 8;
        bitmap = BitmapFactory.decodeStream(is,null, options);
        is.close();
        imageView.setImageBitmap(bitmap);

        return imageView;

    }
    catch (Exception e) {
        e.printStackTrace();

        return null;
    }

我做错了什么？ 谢谢

Answer 1

我相信我已经解决了。请求意图：

Intent intent;
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT){
    intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
    intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
    intent.addFlags(Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION);
}else{
    intent = new Intent(Intent.ACTION_GET_CONTENT);
}
intent.putExtra(Intent.EXTRA_LOCAL_ONLY, true);
intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
intent.setType("image/*");
startActivityForResult(Intent.createChooser(intent, getResources().getString(R.string.form_pick_photos)), REQUEST_PICK_PHOTO);

和onActivityResult

...
// kitkat fixed (broke) content access; to keep the URIs valid over restarts need to persist access permission
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
    final int takeFlags = data.getFlags() & Intent.FLAG_GRANT_READ_URI_PERMISSION;
    ContentResolver resolver = getActivity().getContentResolver();
    for (Uri uri : images) {
        resolver.takePersistableUriPermission(uri, takeFlags);
    }
}
...

我还没有测试过这个 pre-kitkat，我的手机运行的是 5.1，有人可以在旧手机上验证吗？

Answer 2

下面列出的代码，

// kitkat fixed (broke) content access; to keep the URIs valid over restarts need to persist access permission
if(Utils.isKitkat())
{
    final int takeFlags = data.getFlags() & (Intent.FLAG_GRANT_READ_URI_PERMISSION);
    ContentResolver resolver = getActivity().getContentResolver();
    for (Uri uri : images)
    {
        resolver.takePersistableUriPermission(uri, takeFlags);
    }
}

对我来说工作得很好，无论如何我注意到授予我的应用程序的可持久 uri 的最大数量限制为 128。如果我选​​择超过 128 个 uri，我会收到错误：

java.lang.SecurityException: Permission Denial: opening provider........

就在我尝试处理我无法为其保留权限的图像时。你能想出什么解决办法吗？