android - 无法打开内容 : Custom Content Provider

Question

我有两个应用程序，我想从另一个应用程序获取所有图像，假设有 StickerProvider 和 MainActivity 不同的应用

StickerProvider就是ContentProvider，MainActivity有ContentResolver

StickerProvider App 有 Assets 文件夹

资源---->贴纸----------> a.png, b.png

public class StickerProvider extends ContentProvider {

    private final static String LOG_TAG = StickerProvider.class.getName();

    private static final String[] COLUMNS = {
            OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE};

    @Override
    public boolean onCreate() {
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
        /**
         * Source: {@link FileProvider#query(Uri, String[], String, String[], String)} .
         */
        if (projection == null) {
            projection = COLUMNS;
        }

        String[] images = new String[0];
        try {
            images = getContext().getAssets().list("stickers");

            ArrayList<String> listImages = new ArrayList<String>(Arrays.asList(images));

            final MatrixCursor cursor = new MatrixCursor(new String[]{"path"}, 1);
            for (int i = 0; i < listImages.size(); i++) {
                cursor.addRow(new String[]{listImages.get(i)});
            }

            return cursor;

        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    public String getType(Uri uri) {
        /**
         * Source: {@link FileProvider#getType(Uri)} .
         */
        final String file_name = uri.getLastPathSegment();
        final int lastDot = file_name.lastIndexOf('.');
        if (lastDot >= 0) {
            final String extension = file_name.substring(lastDot + 1);
            final String mime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
            if (mime != null) {
                return mime;
            }
        }

        return "image/png";
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        return null;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        return 0;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        return 0;
    }

}

它的 list 文件是

 <provider
            android:name="com.example.StickerProvider"
            android:authorities="com.example"
            android:exported="true"
            android:grantUriPermissions="true"
            android:label="StickerProvider" />

另一个应用程序是 MainActivity ------> 从这里我想获取上述应用程序的所有图像

public class MainActivity extends AppCompatActivity {

    int i=0;
    private static final String TAG = "MainActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ImageView ivOne = (ImageView)findViewById(R.id.ivOne);
        ImageView ivTwo = (ImageView)findViewById(R.id.ivTwo);

        try {
            ContentResolver resolver = getContentResolver();

            Cursor cursor =
                    resolver.query(Uri.parse("content://com.example/stickers"),
                            null,
                            null,
                            null,
                            null);
            if (cursor.moveToFirst()) {
                do {
                    String word = cursor.getString(0);
                    if(i==0){
                        ivOne.setImageURI(Uri.parse("content://com.example/stickers/"+word));
                    }else if(i==1){
                        ivTwo.setImageURI(Uri.parse("content://com.example/stickers/"+word));
                    }
                    // do something meaningful
                    Log.d(TAG, "onCreate: "+word);
                } while (cursor.moveToNext());
            }
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

每当我启动 MainActivity 应用程序时，我都会遇到异常

Unable to open content: content://com.example/a.png
             java.io.FileNotFoundException: No files supported by provider at content://com.example/a.png
                 at android.database.DatabaseUtils.readExceptionWithFileNotFoundExceptionFromParcel(DatabaseUtils.java:144)
                 at android.content.ContentProviderProxy.openTypedAssetFile(ContentProviderNative.java:692)
                 at android.content.ContentResolver.openTypedAssetFileDescriptor(ContentResolver.java:1149)
                 at android.content.ContentResolver.openAssetFileDescriptor(ContentResolver.java:986)
                 at android.content.ContentResolver.openInputStream(ContentResolver.java:706)
                 at android.widget.ImageView.getDrawableFromUri(ImageView.java:900)
                 at android.widget.ImageView.resolveUri(ImageView.java:871)
                 at android.widget.ImageView.setImageURI(ImageView.java:490)
                 at android.support.v7.widget.AppCompatImageView.setImageURI(AppCompatImageView.java:124)
                 at com.pixr.photo.collage.MainActivity.onCreate(MainActivity.java:36)
                 at android.app.Activity.performCreate(Activity.java:6684)
                 at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2652)
                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2766)
                 at android.app.ActivityThread.-wrap12(ActivityThread.java)
                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1507)
                 at android.os.Handler.dispatchMessage(Handler.java:102)
                 at android.os.Looper.loop(Looper.java:154)
                 at android.app.ActivityThread.main(ActivityThread.java:6236)
                 at java.lang.reflect.Method.invoke(Native Method)
                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:891)
                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:781)

Answer 1

ivOne.setImageURI(Uri.parse("content://com.example/stickers/"+word));

您的 ContentProvider 不支持此功能。它没有实现 openFile() 或其任何变体。

或者:

• 使用现有的 ContentProvider 为服务 Assets 提供支持，例如 my StreamProvider ，或者

• 增强您的提供程序以支持 openFile()，就像我在 this sample app 中所做的那样