透过FileProvider再看ContentProvider

<!-- 配置FileProvider-->
<provider
    android:name="androidx.core.content.FileProvider"
    android:authorities="${applicationId}.provider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/provider_paths"/>
</provider>
<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="external" path="."/>
</paths>

//修改文件URL获取方式
Uri photoURI = FileProvider.getUriForFile(context, context.getApplicationContext().getPackageName() + ".provider", createImageFile());

public class FileProvider extends ContentProvider {
    @Override
    public boolean onCreate() {
        return true;
    }
    @Override
    public void attachInfo(@NonNull Context context, @NonNull ProviderInfo info) {
        super.attachInfo(context, info);
        // Sanity check our security
        if (info.exported) {
            throw new SecurityException("Provider must not be exported");
        }
        if (!info.grantUriPermissions) {
            throw new SecurityException("Provider must grant uri permissions");
        }
        mStrategy = getPathStrategy(context, info.authority);
    }
    public static Uri getUriForFile(@NonNull Context context, @NonNull String authority,
            @NonNull File file) {
        final PathStrategy strategy = getPathStrategy(context, authority);
        return strategy.getUriForFile(file);
    }
    @Override
    public Uri insert(@NonNull Uri uri, ContentValues values) {
        throw new UnsupportedOperationException("No external inserts");
    }
    @Override
    public int update(@NonNull Uri uri, ContentValues values, @Nullable String selection,
            @Nullable String[] selectionArgs) {
        throw new UnsupportedOperationException("No external updates");
    }
    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection,
            @Nullable String[] selectionArgs) {
        // ContentProvider has already checked granted permissions
        final File file = mStrategy.getFileForUri(uri);
        return file.delete() ? 1 : 0;
    }
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection,
            @Nullable String[] selectionArgs,
            @Nullable String sortOrder) {
        // ContentProvider has already checked granted permissions
        final File file = mStrategy.getFileForUri(uri);
        if (projection == null) {
            projection = COLUMNS;
        }
        String[] cols = new String[projection.length];
        Object[] values = new Object[projection.length];
        int i = 0;
        for (String col : projection) {
            if (OpenableColumns.DISPLAY_NAME.equals(col)) {
                cols[i] = OpenableColumns.DISPLAY_NAME;
                values[i++] = file.getName();
            } else if (OpenableColumns.SIZE.equals(col)) {
                cols[i] = OpenableColumns.SIZE;
                values[i++] = file.length();
            }
        }
        cols = copyOf(cols, i);
        values = copyOf(values, i);
        final MatrixCursor cursor = new MatrixCursor(cols, 1);
        cursor.addRow(values);
        return cursor;
    }
    @Override
    public String getType(@NonNull Uri uri) {
  final File file = mStrategy.getFileForUri(uri);
        final int lastDot = file.getName().lastIndexOf('.');
        if (lastDot >= 0) {
            final String extension = file.getName().substring(lastDot + 1);
            final String mime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
            if (mime != null) {
                return mime;
            }
        }
        return "application/octet-stream";
    }
}

Cursor cursor = getContentResolver().query(uri, null, null, null, "userid");

<activity  
    android:name=".SecondActivity">  
    <intent-filter>  
        <action android:name=""/>  
        <category android:name=""/>  
        <data android:mimeType="type_test"/> 
    </intent-filter>  
</activity>

@Override
    public String getType(@NonNull Uri uri) {
        return "type_test";
    }
    intent.setData(mContentRUI);  
    startActivity(intent)

if (info.exported) {
            throw new SecurityException("Provider must not be exported");
        }
        if (!info.grantUriPermissions) {
            throw new SecurityException("Provider must grant uri permissions");
        }

<provider
        android:name="com.facebook.internal.FacebookInitProvider"
        android:authorities="${applicationId}.FacebookInitProvider"
        android:exported="false" />

public final class FacebookInitProvider extends ContentProvider {
    private static final String TAG = FacebookInitProvider.class.getSimpleName();
    @Override
    @SuppressWarnings("deprecation")
    public boolean onCreate() {
        try {
            FacebookSdk.sdkInitialize(getContext());
        } catch (Exception ex) {
            Log.i(TAG, "Failed to auto initialize the Facebook SDK", ex);
        }
        return false;
    }
    //...
}

The client app that receives the content URI can open the file and access its contents by calling
 {@link android.content.ContentResolver#openFileDescriptor(Uri, String) ContentResolver.openFileDescriptor} 
 to get a {@link ParcelFileDescriptor}

ParcelFileDescriptor parcelFileDescriptor = getContentResolver().openFileDescriptor(intent.getData(), "r");
FileReader reader = new FileReader(parcelFileDescriptor.getFileDescriptor());
BufferedReader bufferedReader = new BufferedReader(reader);