Show on map: draft via virtual file (with two content providers).

Exported content provider that temporary needs to grant access to the internal content provider.

src/main/java/de/dennisguse/opentracks/content/ShareContentProvider.java

@@ -0,0 +1,175 @@
+package de.dennisguse.opentracks.content;
+
+import android.content.ContentProvider;
+import android.content.ContentValues;
+import android.content.Context;
+import android.content.Intent;
+import android.content.pm.ProviderInfo;
+import android.database.Cursor;
+import android.database.MatrixCursor;
+import android.net.Uri;
+import android.os.Bundle;
+import android.os.ParcelFileDescriptor;
+import android.provider.OpenableColumns;
+import android.util.Log;
+import android.widget.Toast;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.Arrays;
+
+import de.dennisguse.opentracks.BuildConfig;
+import de.dennisguse.opentracks.io.file.TrackFileFormat;
+import de.dennisguse.opentracks.io.file.exporter.FileTrackExporter;
+import de.dennisguse.opentracks.io.file.exporter.TrackWriter;
+
+/**
+ * A content provider that mimics the behavior of {@link androidx.core.content.FileProvider}, which shares virtual (non-existing) files.
+ * The actual content is generated by accessing {@link CustomContentProvider} on request.
+ */
+public class ShareContentProvider extends ContentProvider {
+
+    public static final String TAG = ShareContentProvider.class.getCanonicalName();
+
+    public static final String SHAREPROVIDER = BuildConfig.APPLICATION_ID;
+
+    private static final String[] COLUMNS = {OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE};
+
+    public static String MIME = "application/kml+xml";
+
+    public static Uri createURI(long[] trackIds) {
+        if (trackIds.length == 0) {
+            throw new UnsupportedOperationException();
+        }
+
+        StringBuilder builder = new StringBuilder();
+        for (long trackId : trackIds) {
+            builder.append(trackId).append(",");
+        }
+        builder.deleteCharAt(builder.lastIndexOf(","));
+
+        return Uri.parse("content://" + SHAREPROVIDER + "/" + builder + ".kml");
+    }
+
+    private static long[] parseURI(Uri uri) {
+        String lastPathSegment = uri.getLastPathSegment();
+        if (lastPathSegment == null) {
+            return new long[]{};
+        }
+
+        String[] lastPathSegmentSplit = lastPathSegment.replace(".kml", "").split(",");
+        long[] trackIds = new long[lastPathSegmentSplit.length];
+        for (int i = 0; i < trackIds.length; i++) {
+            trackIds[i] = Long.valueOf(lastPathSegmentSplit[i]);
+        }
+        return trackIds;
+    }
+
+    @Override
+    public boolean onCreate() {
+        return true;
+    }
+
+    @Override
+    public void attachInfo(Context context, ProviderInfo info) {
+        super.attachInfo(context, info);
+        if (!info.grantUriPermissions) {
+            throw new SecurityException("Provider must grant uri permissions");
+        }
+    }
+
+    @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
+        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++] = uri.getLastPathSegment();
+            } else if (OpenableColumns.SIZE.equals(col)) {
+                cols[i] = OpenableColumns.SIZE;
+                values[i++] = -1;
+            }
+        }
+
+        cols = Arrays.copyOf(cols, i);
+        values = Arrays.copyOf(values, i);
+
+        final MatrixCursor cursor = new MatrixCursor(cols, 1);
+        cursor.addRow(values);
+        return cursor;
+    }
+
+    @Nullable
+    @Override
+    public String getType(@NonNull Uri uri) {
+        return MIME;
+    }
+
+    @Nullable
+    @Override
+    public ParcelFileDescriptor openFile(@NonNull Uri uri, @NonNull String mode) throws FileNotFoundException {
+        ContentProviderUtils contentProviderUtils = ContentProviderUtils.Factory.get(getContext());
+
+        final Uri customContentProviderURI = Uri.parse("content://" + ContentProviderUtils.AUTHORITY + "/tracks");
+        getContext().grantUriPermission(getCallingPackage(), customContentProviderURI, Intent.FLAG_GRANT_READ_URI_PERMISSION);
+
+        long[] trackIds = parseURI(uri);
+        final Track[] tracks = new Track[trackIds.length];
+        for (int i = 0; i < trackIds.length; i++) {
+            tracks[i] = contentProviderUtils.getTrack(trackIds[i]);
+        }
+
+        TrackWriter kmlTrackWriter = TrackFileFormat.KML.newTrackWriter(getContext(), false);
+        final FileTrackExporter fileTrackExporter = new FileTrackExporter(contentProviderUtils, tracks, kmlTrackWriter, null);
+
+        PipeDataWriter pipeDataWriter = new PipeDataWriter<String>() {
+            @Override
+            public void writeDataToPipe(@NonNull ParcelFileDescriptor output, @NonNull Uri uri, @NonNull String mimeType, @Nullable Bundle opts, @Nullable String args) {
+                try (FileOutputStream fileOutputStream = new FileOutputStream(output.getFileDescriptor())) {
+                    fileTrackExporter.writeTrack(fileOutputStream);
+                } catch (IOException e) {
+                    Log.w(TAG, "Oops closing " + e);
+                    Toast.makeText(getContext(), "", Toast.LENGTH_SHORT).show();
+                } finally {
+
+                    getContext().revokeUriPermission(customContentProviderURI, Intent.FLAG_GRANT_READ_URI_PERMISSION);
+                }
+            }
+        };
+
+        return openPipeHelper(uri, getType(uri), null, null, pipeDataWriter);
+    }
+
+    @Nullable
+    @Override
+    public String[] getStreamTypes(@NonNull Uri uri, @NonNull String mimeTypeFilter) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Nullable
+    @Override
+    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
+        throw new UnsupportedOperationException();
+    }
+}