理解RemoteViews
什么是remoteViews？按照字面意思是遠程View，但RemoteViews并沒有繼承View，而是繼承Object。它的作用是可以跨進程更新界面，聽起來有點神奇。RemoteViews在Android中的使用場景有兩種：通知欄和桌面小部件
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RemoteViews的應用
1.在通知欄上的應用
①使用系統默認的樣式彈出通知
Notification notification= new Notification();
notification.icon = R.drawable.notify;
notification.when = System.currentTimeMillis();
notification.tickerText = "通知";
notification.flags = Notification.FLAG_AUTO_CANCEL;
//創建延時意圖
Intent intent = new Intent(this, OtherActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent,
PendingIntent.FLAG_UPDATE_CURRENT);
notification.setLatestEventInfo(this,"通知", "具體內容", pendingIntent):
NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
nm.notify(0, notification);
②使用RemoteViews可以自定義布局，通過RemoteViews來加載布局文件即可改變通知的樣式，具體代碼如下
Notification notification= new Notification();
notification.icon = R.drawable.notify;
notification.when = System.currentTimeMillis();
notification.tickerText = "通知";
notification.flags = Notification.FLAG_AUTO_CANCEL;
//創建延時意圖
Intent intent = new Intent(this, OtherActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent,
PendingIntent.FLAG_UPDATE_CURRENT);
RemoteViews remoteViews = new RemoteViews(getPackageName(), R.layout.layout_notification);
remoteViews.setTextViewText(R.id.msg, "自定義通知");
remoteViews.setImageViewResource(R.id.icon, R.drawable.icon);
PendingIntent pendingIntent2 = PendingIntent.getActivity(this, 0,
new Intent(this, SecondActivity.class), PendingIntent.FLAG_UPDATE_CURRENT);
remoteViews.setOnClickPendingIntent(R.id.btn, pendingIntent2);
notification.contentView = remoteViews;
notification.contentIntent = pendingIntent;
NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
nm.notify(1, notification);
2.在桌面小部件上的應用
AppWidgetProvider是Android中提供的用于實現桌面小部件的類，實際上是一個廣播。具體實現步驟如下
①定義小部件界面
自定義xml布局文件，具體布局樣式根據實際開發需要，如widget.xml
②定義小部件配置信息
在res/xml下新建appwidget_provider_info.xml，名稱任意
<xml version="1.0" encoding="utf-8">
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
android:initialLayout="@layout/widget"
android:minHeght="84dp"
android:minWidth="84dp"
android:updatePeriodMillis="86400000" >
</appwidget-provider>
③定義小部件的實現類
public class MyAppWidgetProvider extends AppWidgetProvider {
private static final String CLICK_ACTION = "com.hj.action.click";
@Override
public void onReceive(final Context context, Intent intent) {
super.onReceive(context, intent);
if (intent.getAction().equals(CLICK_ACTION)) {
new Thread(new Runnable() {
@Override
public void run() {
Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(),
R.drawable.ic_launcher_v2);
AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);
for (int i = 0; i < 10; i++) {
float degree = (i * 10) % 360;
RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.widget);
remoteViews.setImageViewBitmap(R.id.container, rotateBitmap(context, bitmap, degree));
Intent intent1 = new Intent(CLICK_ACTION);
PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intent1, 0);
remoteViews.setOnClickPendingIntent(R.id.container, pendingIntent);
appWidgetManager.updateAppWidget(new ComponentName(context, MyAppWidgetProvider.class), remoteViews);
SystemClock.sleep(30);
}
}
}).start();
}
}
@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
super.onUpdate(context, appWidgetManager, appWidgetIds);
int count = appWidgetIds.length; for (int i = 0; i < count; i++) {
int appWidgetId = appWidgetIds[i];
onWidgetUpdate(context, appWidgetManager, appWidgetId);
}
}
private void onWidgetUpdate(Context context, AppWidgetManager appWidgetManager, int appWidgetId) {
RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.widget);
Intent intent = new Intent();
intent.setAction(CLICK_ACTION);
PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intent, 0);
remoteViews.setOnClickPendingIntent(R.id.container, pendingIntent);
appWidgetManager.updateAppWidget(appWidgetId, remoteViews);
}
private Bitmap rotateBitmap(Context context, Bitmap bitmap, float degree) {
Matrix matrix = new Matrix();
matrix.reset();
matrix.setRotate(degree);
Bitmap tmpBitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
bitmap.getHeight(), matrix, true);
return tmpBitmap;
}
}
④在AndroidManifest.xml聲明小部件
桌面部件實際上是一個廣播組件，必須要注冊。APPWIDGET_UPDATE代表該廣播是作為小部件的標識存在的
<receiver
android:name=".MyAppWidgetProvider>
<meta-data
android:name="android.appwidget.provider"
android:resource="@xml/appwidget_provider_info">
<intent-filter>
<action android:name="com.hj.action.click"/>
<action android:name="android.appwidget.action.APPWIDGET_UPDATE"/>
</intent-filter>
</receiver>
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PendingIntent
PendingIntent表示一種處于pending狀態的意圖，而pending狀態表示的是一種待定、等待、即將發生的意思。PendingIntent支持三種待定意圖：啟動Activity、啟動Service和發送廣播。
1.PendingIntent的Flag介紹
FLAG_ONE_SHOT
PendingIntent只能被使用一次，然后會自動cancel；如果后續還有相同的PendingIntent，那么他們的send方法就會調用失敗
FLAG_NO_CREATE
PendingIntent不會主動創建，如果當前PendingIntent不存在，那么三種意圖方法調用會直接返回null，獲取PendingIntent會失敗，它無法單獨使用
FLAG_CANCEL_CURRENT
PendingIntent如果已經存在，那么它們都會被cancle，然后系統會創建一個新的PendingIntent。對于通知欄而言，那些被cancel的消息單擊后無法打開
FLAG_UPDATE_CURRENT
PendingIntent如果已經存在，那么它們都會被更新
通知欄而言，notify(int, notification)方法中，若id值每次都不同的話，需要考慮到flag參數對應消息接收的情況
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RemoteViews內部機制
RemoteViews目前并不能支持所有的View的類型，不能支持自定義View、EditText等，同時沒有提供findViewById方法，無法直接訪問View元素。RemoteViews會通過Binder傳遞到SystemServer進程，系統會通過RemoteViews中包名等信息去得到該應用的資源并加載布局文件，當需要更新RemoteViews時，我們需要通過一系列set方法并通過NotificationManager和AppWidgetManager來提交更新任務，具體的更新操作也是在SystemServer進程中完成的。RemoteViews提供一個Action的概念，Action代表一個View操作，系統首先將View操作封裝到Action對象并跨進程傳輸到遠程進程，接著在遠程進程中執行Action對象中的具體操作
