Add API demo for monitoring media content.

Both the classic ContentObserver API, and the new
JobScheduler API.

Change-Id: I2011389abb2f863e810ccc9012fb3c53c93c76fd

samples/ApiDemos/src/com/example/android/apis/content/MediaContentJob.java

@@ -0,0 +1,114 @@
+/**
+ * Copyright (c) 2016, 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 com.example.android.apis.content;
+
+import android.app.job.JobInfo;
+import android.app.job.JobParameters;
+import android.app.job.JobScheduler;
+import android.app.job.JobService;
+import android.content.ComponentName;
+import android.content.Context;
+import android.net.Uri;
+import android.os.Handler;
+import android.provider.MediaStore;
+import android.widget.Toast;
+
+import com.example.android.apis.R;
+
+import java.util.List;
+
+/**
+ * Stub job to execute when there is a change to any media: content URI.
+ */
+public class MediaContentJob extends JobService {
+    static final Uri MEDIA_URI = Uri.parse("content://" + MediaStore.AUTHORITY + "/");
+
+    final Handler mHandler = new Handler();
+    final Runnable mWorker = new Runnable() {
+        @Override public void run() {
+            scheduleJob(MediaContentJob.this);
+            jobFinished(mRunningParams, false);
+        }
+    };
+
+    JobParameters mRunningParams;
+
+    public static void scheduleJob(Context context) {
+        JobScheduler js = context.getSystemService(JobScheduler.class);
+        JobInfo.Builder builder = new JobInfo.Builder(R.id.schedule_job,
+                new ComponentName(context, MediaContentJob.class));
+        builder.addTriggerContentUri(new JobInfo.TriggerContentUri(MEDIA_URI,
+                JobInfo.TriggerContentUri.FLAG_NOTIFY_FOR_DESCENDANTS));
+        js.schedule(builder.build());
+    }
+
+    public static boolean isScheduled(Context context) {
+        JobScheduler js = context.getSystemService(JobScheduler.class);
+        List<JobInfo> jobs = js.getAllPendingJobs();
+        if (jobs == null) {
+            return false;
+        }
+        for (int i=0; i<jobs.size(); i++) {
+            if (jobs.get(i).getId() == R.id.schedule_job) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public static void cancelJob(Context context) {
+        JobScheduler js = context.getSystemService(JobScheduler.class);
+        js.cancel(R.id.schedule_job);
+    }
+
+    @Override
+    public boolean onStartJob(JobParameters params) {
+        mRunningParams = params;
+        StringBuilder sb = new StringBuilder();
+        sb.append("Media content has changed:\n");
+        if (params.getTriggeredContentAuthorities() != null) {
+            sb.append("Authorities: ");
+            boolean first = true;
+            for (String auth : params.getTriggeredContentAuthorities()) {
+                if (first) {
+                    first = false;
+                } else {
+                    sb.append(", ");
+                }
+                sb.append(auth);
+            }
+            if (params.getTriggeredContentUris() != null) {
+                for (Uri uri : params.getTriggeredContentUris()) {
+                    sb.append("\n");
+                    sb.append(uri);
+                }
+            }
+        } else {
+            sb.append("(No content)");
+        }
+        Toast.makeText(this, sb.toString(), Toast.LENGTH_LONG).show();
+        // We will emulate taking some time to do this work, so we can see batching happen.
+        mHandler.postDelayed(mWorker, 20*1000);
+        return true;
+    }
+
+    @Override
+    public boolean onStopJob(JobParameters params) {
+        mHandler.removeCallbacks(mWorker);
+        return false;
+    }
+}

samples/ApiDemos/src/com/example/android/apis/content/MediaContentObserver.java

@@ -0,0 +1,92 @@
+/**
+ * Copyright (c) 2016, 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 com.example.android.apis.content;
+
+import android.app.Activity;
+import android.database.ContentObserver;
+import android.net.Uri;
+import android.os.Bundle;
+import android.os.Handler;
+import android.util.Log;
+import android.view.View;
+import android.widget.TextView;
+
+import com.example.android.apis.R;
+
+public class MediaContentObserver extends Activity {
+    ContentObserver mContentObserver;
+    View mScheduleJob;
+    View mCancelJob;
+    TextView mDataText;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        mContentObserver = new ContentObserver(new Handler()) {
+            public void onChange(boolean selfChange, Uri uri) {
+                mDataText.append(uri.toString());
+                mDataText.append("\n");
+            }
+        };
+
+        Log.d("foo", "Observing: " + MediaContentJob.MEDIA_URI);
+
+        // See res/any/layout/resources.xml for this view layout definition.
+        setContentView(R.layout.media_content_observer);
+
+        mScheduleJob = findViewById(R.id.schedule_job);
+        mCancelJob = findViewById(R.id.cancel_job);
+        mDataText = (TextView)findViewById(R.id.changes_text);
+
+        mScheduleJob.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                MediaContentJob.scheduleJob(MediaContentObserver.this);
+                updateButtons();
+            }
+        });
+        mCancelJob.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                MediaContentJob.cancelJob(MediaContentObserver.this);
+                updateButtons();
+            }
+        });
+        updateButtons();
+
+        getContentResolver().registerContentObserver(MediaContentJob.MEDIA_URI, true,
+                mContentObserver);
+    }
+
+    void updateButtons() {
+        if (MediaContentJob.isScheduled(this)) {
+            mScheduleJob.setEnabled(false);
+            mCancelJob.setEnabled(true);
+        } else {
+            mScheduleJob.setEnabled(true);
+            mCancelJob.setEnabled(false);
+        }
+    }
+
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
+        getContentResolver().unregisterContentObserver(mContentObserver);
+    }
+
+}