beef up the syncadapter API

1 files changed, 176 insertions, 0 deletions

diff --git a/core/java/android/content/AbstractThreadedSyncAdapter.java b/core/java/android/content/AbstractThreadedSyncAdapter.java
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index 0000000..f15a902
--- /dev/null
+++ b/core/java/android/content/AbstractThreadedSyncAdapter.java
@@ -0,0 +1,176 @@
+/*
+ * Copyright (C) 2009 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.content;
+
+import android.accounts.Account;
+import android.os.Bundle;
+import android.os.Process;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * An abstract implementation of a SyncAdapter that spawns a thread to invoke a sync operation.
+ * If a sync operation is already in progress when a startSync() request is received then an error
+ * will be returned to the new request and the existing request will be allowed to continue.
+ * When a startSync() is received and there is no sync operation in progress then a thread
+ * will be started to run the operation and {@link #performSync} will be invoked on that thread.
+ * If a cancelSync() is received that matches an existing sync operation then the thread
+ * that is running that sync operation will be interrupted, which will indicate to the thread
+ * that the sync has been canceled.
+ *
+ * @hide
+ */
+public abstract class AbstractThreadedSyncAdapter {
+    private final Context mContext;
+    private final AtomicInteger mNumSyncStarts;
+    private final ISyncAdapterImpl mISyncAdapterImpl;
+
+    // all accesses to this member variable must be synchronized on "this"
+    private SyncThread mSyncThread;
+
+    /** Kernel event log tag.  Also listed in data/etc/event-log-tags. */
+    public static final int LOG_SYNC_DETAILS = 2743;
+
+    /**
+     * Creates an {@link AbstractThreadedSyncAdapter}.
+     * @param context the {@link Context} that this is running within.
+     */
+    public AbstractThreadedSyncAdapter(Context context) {
+        mContext = context;
+        mISyncAdapterImpl = new ISyncAdapterImpl();
+        mNumSyncStarts = new AtomicInteger(0);
+        mSyncThread = null;
+    }
+
+    class ISyncAdapterImpl extends ISyncAdapter.Stub {
+        public void startSync(ISyncContext syncContext, String authority, Account account,
+                Bundle extras) {
+            final SyncContext syncContextClient = new SyncContext(syncContext);
+
+            boolean alreadyInProgress;
+            // synchronize to make sure that mSyncThread doesn't change between when we
+            // check it and when we use it
+            synchronized (this) {
+                if (mSyncThread == null) {
+                    mSyncThread = new SyncThread(
+                            "SyncAdapterThread-" + mNumSyncStarts.incrementAndGet(),
+                            syncContextClient, authority, account, extras);
+                    Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
+                    mSyncThread.start();
+                    alreadyInProgress = false;
+                } else {
+                    alreadyInProgress = true;
+                }
+            }
+
+            // do this outside since we don't want to call back into the syncContext while
+            // holding the synchronization lock
+            if (alreadyInProgress) {
+                syncContextClient.onFinished(SyncResult.ALREADY_IN_PROGRESS);
+            }
+        }
+
+        public void cancelSync(ISyncContext syncContext) {
+            // synchronize to make sure that mSyncThread doesn't change between when we
+            // check it and when we use it
+            synchronized (this) {
+                if (mSyncThread != null
+                        && mSyncThread.mSyncContext.getISyncContext() == syncContext) {
+                    mSyncThread.interrupt();
+                }
+            }
+        }
+    }
+
+    /**
+     * The thread that invokes performSync(). It also acquires the provider for this sync
+     * before calling performSync and releases it afterwards. Cancel this thread in order to
+     * cancel the sync.
+     */
+    private class SyncThread extends Thread {
+        private final SyncContext mSyncContext;
+        private final String mAuthority;
+        private final Account mAccount;
+        private final Bundle mExtras;
+
+        private SyncThread(String name, SyncContext syncContext, String authority,
+                Account account, Bundle extras) {
+            super(name);
+            mSyncContext = syncContext;
+            mAuthority = authority;
+            mAccount = account;
+            mExtras = extras;
+        }
+
+        public void run() {
+            if (isCanceled()) {
+                return;
+            }
+
+            SyncResult syncResult = new SyncResult();
+            ContentProviderClient provider = null;
+            try {
+                provider = mContext.getContentResolver().acquireContentProviderClient(mAuthority);
+                if (provider != null) {
+                    AbstractThreadedSyncAdapter.this.performSync(mAccount, mExtras,
+                            mAuthority, provider, syncResult);
+                } else {
+                    // TODO(fredq) update the syncResults to indicate that we were unable to
+                    // find the provider. maybe with a ProviderError?
+                }
+            } finally {
+                if (provider != null) {
+                    provider.release();
+                }
+                if (!isCanceled()) {
+                    mSyncContext.onFinished(syncResult);
+                }
+                // synchronize so that the assignment will be seen by other threads
+                // that also synchronize accesses to mSyncThread
+                synchronized (this) {
+                    mSyncThread = null;
+                }
+            }
+        }
+
+        private boolean isCanceled() {
+            return Thread.currentThread().isInterrupted();
+        }
+    }
+
+    /**
+     * @return a reference to the ISyncAdapter interface into this SyncAdapter implementation.
+     */
+    public final ISyncAdapter getISyncAdapter() {
+        return mISyncAdapterImpl;
+    }
+
+    /**
+     * Perform a sync for this account. SyncAdapter-specific parameters may
+     * be specified in extras, which is guaranteed to not be null. Invocations
+     * of this method are guaranteed to be serialized.
+     *
+     * @param account the account that should be synced
+     * @param extras SyncAdapter-specific parameters
+     * @param authority the authority of this sync request
+     * @param provider a ContentProviderClient that points to the ContentProvider for this
+     *   authority
+     * @param syncResult SyncAdapter-specific parameters
+     */
+    public abstract void performSync(Account account, Bundle extras,
+            String authority, ContentProviderClient provider, SyncResult syncResult);
+}
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