Android通知Notification

Notification 是在 App 常规 UI 之外提示事件的交互：用户可以在用别的 app 时看到通知，方便时再点进去。下面覆盖 Builder 发布、更新与移除、从通知启动 Activity 时保留返回栈、进度条通知，以及 RemoteViews 自定义界面。

一、建立一个 Notification

用 NotificationCompat.Builder 设 UI 特征和行为，再 notify(id, notification) 发布。notificationId 唯一标识这条通知。

NotificationCompat.Builder builder = new NotificationCompat.Builder(this);
builder.setSmallIcon(R.drawable.m4);
builder.setContentTitle("通知标题");
builder.setContentText("1条新消息");
builder.setTicker("收到1条新消息");
builder.setNumber(1);
builder.setAutoCancel(true);
builder.setDefaults(Notification.DEFAULT_ALL); // requires VIBRATE permission
builder.setWhen(System.currentTimeMillis());
builder.setSound(uri);

Intent intent = new Intent(this, BaseActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
builder.setContentIntent(pendingIntent);

NotificationManager mNotifyManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
Notification notification = builder.build();
int notificationId = 10;
mNotifyManager.notify(notificationId, notification);

PendingIntent 字面是「等待的、未决定的 Intent」。静态工厂 getActivity / getBroadcast / getService 分别对应跳 Activity、开广播、开服务，都必须传入 Intent 和 Context。

二、更新与移除

发布时用固定 ID：notify(ID, notification)。之后改 Builder 再 build()，用同一个 ID 发布即更新。

移除：创建时 setAutoCancel(true)，点击即消失；或 cancel(notificationId) / cancelAll()。

三、从通知启动时保留导航

通知打开的是工作流中的某个 Activity 时，要在 manifest 声明层次，再用 TaskStackBuilder 组返回栈。

1. Manifest 层次：

<activity
    android:name=".MainActivity"
    android:label="@string/app_name" >
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>
<activity
    android:name=".ResultActivity"
    android:parentActivityName=".MainActivity">
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value=".MainActivity"/>
</activity>

2. 为启动 Intent 创建返回栈：

int id = 1;
Intent resultIntent = new Intent(this, ResultActivity.class);
TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);
stackBuilder.addParentStack(ResultActivity.class);
stackBuilder.addNextIntent(resultIntent);
PendingIntent resultPendingIntent =
        stackBuilder.getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);

NotificationCompat.Builder builder = new NotificationCompat.Builder(this);
builder.setContentIntent(resultPendingIntent);
NotificationManager mNotificationManager =
        (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
mNotificationManager.notify(id, builder.build());

四、在通知里展示进度

确定进度：setProgress(max, progress, false)；不确定则第三个参数为 true。完成时 setProgress(0, 0, false) 去掉进度条。进度变化要不断改 progress 并再次 notify。

int id = 1;
mNotifyManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
mBuilder = new NotificationCompat.Builder(this);
mBuilder.setContentTitle("Picture Download")
    .setContentText("Download in progress")
    .setSmallIcon(R.drawable.ic_notification);
new Thread(new Runnable() {
    @Override
    public void run() {
        int incr;
        for (incr = 0; incr <= 100; incr+=5) {
            mBuilder.setProgress(100, incr, false);
            mNotifyManager.notify(id, mBuilder.build());
            try {
                Thread.sleep(5*1000);
            } catch (InterruptedException e) {
                Log.d(TAG, "sleep failure");
            }
        }
        mBuilder.setContentText("Download complete")
                .setProgress(0,0,false);
        mNotifyManager.notify(id, mBuilder.build());
    }
}).start();

五、自定义 Notification 界面

RemoteViews 铺自定义布局，setOnClickPendingIntent 绑点击。

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this);
mBuilder.setSmallIcon(R.drawable.m8);
mBuilder.setTicker("自定义通知，你有新消息");
mBuilder.setAutoCancel(true);

RemoteViews view = new RemoteViews(getPackageName(), R.layout.view_notificaction_layout);
mBuilder.setContent(view);

Intent intent = new Intent(this, RadioTabActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 01, intent, PendingIntent.FLAG_UPDATE_CURRENT);
view.setOnClickPendingIntent(R.id.player_notification, pendingIntent);

Notification notification = mBuilder.build();
int notificationId = 29;
NotificationManager mNotifyManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
mNotifyManager.notify(notificationId, notification);

一句话总结：NotificationCompat.Builder 配 UI + PendingIntent，同一 ID 再 notify 即更新；要返回栈用 TaskStackBuilder，要进度反复 setProgress，要自定义界面用 RemoteViews。