Implement a cancelation mechanism for queries.
Added new API to enable cancelation of SQLite and content provider
queries by means of a CancelationSignal object. The application
creates a CancelationSignal object and passes it as an argument
to the query. The cancelation signal can then be used to cancel
the query while it is executing.
If the cancelation signal is raised before the query is executed,
then it is immediately terminated.
Change-Id: If2c76e9a7e56ea5e98768b6d4f225f0a1ca61c61
diff --git a/core/java/android/content/ContentProvider.java b/core/java/android/content/ContentProvider.java
index 116ca48..adbeb6a 100644
--- a/core/java/android/content/ContentProvider.java
+++ b/core/java/android/content/ContentProvider.java
@@ -29,6 +29,7 @@
import android.os.Bundle;
import android.os.ParcelFileDescriptor;
import android.os.Process;
+import android.os.RemoteException;
import android.util.Log;
import java.io.File;
@@ -174,28 +175,33 @@
return getContentProvider().getClass().getName();
}
+ @Override
public Cursor query(Uri uri, String[] projection,
- String selection, String[] selectionArgs, String sortOrder) {
+ String selection, String[] selectionArgs, String sortOrder,
+ ICancelationSignal cancelationSignal) {
enforceReadPermission(uri);
- return ContentProvider.this.query(uri, projection, selection,
- selectionArgs, sortOrder);
+ return ContentProvider.this.query(uri, projection, selection, selectionArgs, sortOrder,
+ CancelationSignal.fromTransport(cancelationSignal));
}
+ @Override
public String getType(Uri uri) {
return ContentProvider.this.getType(uri);
}
-
+ @Override
public Uri insert(Uri uri, ContentValues initialValues) {
enforceWritePermission(uri);
return ContentProvider.this.insert(uri, initialValues);
}
+ @Override
public int bulkInsert(Uri uri, ContentValues[] initialValues) {
enforceWritePermission(uri);
return ContentProvider.this.bulkInsert(uri, initialValues);
}
+ @Override
public ContentProviderResult[] applyBatch(ArrayList<ContentProviderOperation> operations)
throws OperationApplicationException {
for (ContentProviderOperation operation : operations) {
@@ -210,17 +216,20 @@
return ContentProvider.this.applyBatch(operations);
}
+ @Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
enforceWritePermission(uri);
return ContentProvider.this.delete(uri, selection, selectionArgs);
}
+ @Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
enforceWritePermission(uri);
return ContentProvider.this.update(uri, values, selection, selectionArgs);
}
+ @Override
public ParcelFileDescriptor openFile(Uri uri, String mode)
throws FileNotFoundException {
if (mode != null && mode.startsWith("rw")) enforceWritePermission(uri);
@@ -228,6 +237,7 @@
return ContentProvider.this.openFile(uri, mode);
}
+ @Override
public AssetFileDescriptor openAssetFile(Uri uri, String mode)
throws FileNotFoundException {
if (mode != null && mode.startsWith("rw")) enforceWritePermission(uri);
@@ -235,6 +245,7 @@
return ContentProvider.this.openAssetFile(uri, mode);
}
+ @Override
public Bundle call(String method, String arg, Bundle extras) {
return ContentProvider.this.call(method, arg, extras);
}
@@ -251,6 +262,11 @@
return ContentProvider.this.openTypedAssetFile(uri, mimeType, opts);
}
+ @Override
+ public ICancelationSignal createCancelationSignal() throws RemoteException {
+ return CancelationSignal.createTransport();
+ }
+
private void enforceReadPermission(Uri uri) {
final int uid = Binder.getCallingUid();
if (uid == mMyUid) {
@@ -541,6 +557,75 @@
String selection, String[] selectionArgs, String sortOrder);
/**
+ * Implement this to handle query requests from clients with support for cancelation.
+ * This method can be called from multiple threads, as described in
+ * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html#Threads">Processes
+ * and Threads</a>.
+ * <p>
+ * Example client call:<p>
+ * <pre>// Request a specific record.
+ * Cursor managedCursor = managedQuery(
+ ContentUris.withAppendedId(Contacts.People.CONTENT_URI, 2),
+ projection, // Which columns to return.
+ null, // WHERE clause.
+ null, // WHERE clause value substitution
+ People.NAME + " ASC"); // Sort order.</pre>
+ * Example implementation:<p>
+ * <pre>// SQLiteQueryBuilder is a helper class that creates the
+ // proper SQL syntax for us.
+ SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder();
+
+ // Set the table we're querying.
+ qBuilder.setTables(DATABASE_TABLE_NAME);
+
+ // If the query ends in a specific record number, we're
+ // being asked for a specific record, so set the
+ // WHERE clause in our query.
+ if((URI_MATCHER.match(uri)) == SPECIFIC_MESSAGE){
+ qBuilder.appendWhere("_id=" + uri.getPathLeafId());
+ }
+
+ // Make the query.
+ Cursor c = qBuilder.query(mDb,
+ projection,
+ selection,
+ selectionArgs,
+ groupBy,
+ having,
+ sortOrder);
+ c.setNotificationUri(getContext().getContentResolver(), uri);
+ return c;</pre>
+ * <p>
+ * If you implement this method then you must also implement the version of
+ * {@link #query(Uri, String[], String, String[], String)} that does not take a cancelation
+ * provider to ensure correct operation on older versions of the Android Framework in
+ * which the cancelation signal overload was not available.
+ *
+ * @param uri The URI to query. This will be the full URI sent by the client;
+ * if the client is requesting a specific record, the URI will end in a record number
+ * that the implementation should parse and add to a WHERE or HAVING clause, specifying
+ * that _id value.
+ * @param projection The list of columns to put into the cursor. If
+ * null all columns are included.
+ * @param selection A selection criteria to apply when filtering rows.
+ * If null then all rows are included.
+ * @param selectionArgs You may include ?s in selection, which will be replaced by
+ * the values from selectionArgs, in order that they appear in the selection.
+ * The values will be bound as Strings.
+ * @param sortOrder How the rows in the cursor should be sorted.
+ * If null then the provider is free to define the sort order.
+ * @param cancelationSignal A signal to cancel the operation in progress, or null if none.
+ * If the operation is canceled, then {@link OperationCanceledException} will be thrown
+ * when the query is executed.
+ * @return a Cursor or null.
+ */
+ public Cursor query(Uri uri, String[] projection,
+ String selection, String[] selectionArgs, String sortOrder,
+ CancelationSignal cancelationSignal) {
+ return query(uri, projection, selection, selectionArgs, sortOrder);
+ }
+
+ /**
* Implement this to handle requests for the MIME type of the data at the
* given URI. The returned MIME type should start with
* <code>vnd.android.cursor.item</code> for a single record,