完全理解顶峰APP开发Android系列中的RemoteViews.doc

完全理解顶峰APP开发Android系列中的RemoteViews一、什么是RemoteViewsRemoteViews翻译过来就是远程视图.顾名思义,RemoteViews不是当前进程的View,是属于SystemServer进程.应用程序与RemoteViews之间依赖Binder实现了进程间通信.二、RemoteViews的用法RemoteViews使用最多的场合是通知栏和桌面小插件. 以通知栏为例,讲解下它的用法.1、新建一个Notification这里要注意是在android3.0之前都是使用如下的形式构建一个Notification / 1.新建一个Notification对象 Notification mNotification = new Notification(); / 2.添加属性,比如标题、内容、优先级、图片等 mNotification.tickerText = 这是通知栏的标题; mNotification.icon = R.drawable.ic_launcher; mNotification.flags=Notification.FLAG_NO_CLEAR; mNotification.setLatestEventInfo(this, 这是内容, 这是标题, null);在3.0之后官方推荐使用建造者模式创建Notification.Notification mNotification = new Notification.Builder(this) .setContentTitle(这是标题 ) .setContentText(这是内容) .setSmallIcon(R.drawable.ic_launcher) .build();Notification有很多属性,这里列举一些 - setContentTitle 设置标题 - setContentText 设置内容 - setLargeIcon 设置通知栏大图标 - setSmallIcon 设置通知栏小图标 - setContent 设置RemoteViews - setContentIntent 当通知条目被点击，就执行这个被设置的Intent. - setDeleteIntent 当用户点击Clear All Notifications按钮区删除所有的通知的时候，这个被设置的Intent被执行 - setLights 设置闪光灯 - setSound 设置声音 - setPriority 设置优先级2、设置Notification的RemoteViews如果要给通知栏使用自定义布局就要使用RemoteViews了,传入包名和相应的布局.RemoteViews mRemoteViews=new RemoteViews(com.example.remoteviewdemo, R.layout.remoteview_layout);然后通过setContent()传入RemoteViews 对象即可.这里顺便讲一下PendingIntent,PendingIntent是”延迟意图”的意思,就是当满足某一条件时出触发这个Intent.通过PendingIntent的getActivity、getBroadcast、getService等分别构建一个打开对应组件的延迟Intent. 传入四个参数，context、intent、requestCode(自定义)、flag.Intent intent=new Intent(MainActivity.this,MainActivity.class);PendingIntent mPendingIntent=PendingIntent.getActivity(MainActivity.this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);PendingIntent有4种flag. - FLAG_ONE_SHOT 只执行一次 - FLAG_NO_CREATE 若描述的Intent不存在则返回NULL值 - FLAG_CANCEL_CURRENT 如果描述的PendingIntent已经存在，则在产生新的Intent之前会先取消掉当前的 - FLAG_UPDATE_CURRENT 总是执行,这个flag用的最多3、获取通知管理者NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);4、弹出通知调用notify方法,传入一个id(自定义)和通知实例即可.manager.notify(1, mNotification);5、例子我用一个按钮弹出通知,点击这个通知时进入到该Activitypublic class MainActivity extends Activity private NotificationManager manager; private Notification mNotification; Override protected void onCreate(Bundle savedInstanceState) super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); /1.创建RemoteViews实例 RemoteViews mRemoteViews=new RemoteViews(com.example.remoteviewdemo, R.layout.remoteview_layout); /2.构建一个打开Activity的PendingIntent Intent intent=new Intent(MainActivity.this,MainActivity.class); PendingIntent mPendingIntent=PendingIntent.getActivity(MainActivity.this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT); /3.创建一个Notification mNotification = new Notification.Builder(this) .setSmallIcon(R.drawable.ic_launcher) .setContentIntent(mPendingIntent) .setContent(mRemoteViews) .build(); /4.获取NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE); Button button1 = (Button) findViewById(R.id.button1); button1.setOnClickListener(new OnClickListener() Override public void onClick(View v) /弹出通知 manager.notify(1, mNotification); ); 6、改变RemoteViews的布局RemoteViews并不能直接获得控件实例,然后对控件进行操作.它提供了 setTextViewText(viewId, text)、setImageViewResource(viewId, srcId)等方法进行操作,传入控件id和相应的修改内容. 列举一下常用的属性 - setTextViewText(viewId, text) 设置文本 - setTextColor(viewId, color) 设置文本颜色 - setTextViewTextSize(viewId, units, size) 设置文本大小 - setImageViewBitmap(viewId, bitmap) 设置图片 - setImageViewResource(viewId, srcId) 根据图片资源设置图片 - setViewPadding(viewId, left, top, right, bottom) 设置Padding间距 - setOnClickPendingIntent(viewId, pendingIntent) 设置点击事件 我这里就以setTextViewText改变文本的属性来讲解改变RemoteViews的原理. 我在原来的代码上加上一个按钮点击改变内容Button button2 = (Button) findViewById(R.id.button2);button2.setOnClickListener(new OnClickListener() Override public void onClick(View v) mRemoteViews.setTextViewText(R.id.remote_content, 改变了内容); manager.notify(1, mNotification); );三、RemoteViews的改变原理1.setTextViewText方法代码如下public class RemoteViews implements Parcelable, Filter .public void setTextViewText(int viewId, CharSequence text) setCharSequence(viewId, setText, text); . 2.调用了setCharSequence方法3.在setCharSequence方法里调用了addAction方法,传入一个ReflectionAction实例，ReflectionAction继承自Action,它是用反射调用的private final class ReflectionAction extends Action . ReflectionAction(int viewId, String methodName, int type, Object value) this.viewId = viewId; this.methodName = methodName; this.type = type; this.value = value; . 4.看下addAction方法，用了一个集合来保存Action实例,然后更新已使用内存的统计情况public class RemoteViews implements Parcelable, Filter .private void addAction(Action a) if (mActions = null) mActions = new ArrayList(); /添加Action mActions.add(a); / 更新已使用内存的统计情况 a.updateMemoryUsageEstimate(mMemoryUsageCounter); . 这一步之后,会调用1 manager.notify(1, mNotification);来更新,追踪这个notify方法.public class NotificationManager .public void notify(String tag, int id, Notification notification) . INotificationManager service = getService(); try service.enqueueNotificationWithTag(pkg, mContext.getOpPackageName(), tag, id, stripped, idOut, UserHandle.myUserId(); . . 5.上面会调用getService方法返回INotificationManager这个系统服务,它是在SystemServer进程添加的.然后该服务调用 enqueueNotificationWithTag方法最后层层调用到public class NotificationManagerService extends INotificationManager.Stub .StatusBarNotification n = new StatusBarNotification(pkg, id, tag, r.uid, r.initialPid, notification);try mStatusBar.updateNotification(r.statusBarKey, n) . 新建了StatusBarNotification实例,然后调用updateNotification方法. 这个方法会进入到public class PhoneStatusBar extends StatusBar .public void updateNotification(IBinder key, StatusBarNotification notification) . final RemoteViews contentView = notification.notification.contentView; . contentView.reapply(mContext, oldEntry.content); . 会调用StatusBarNotification 的notification.contentView返回RemoteViews 对象,然后调用reapply方法.6.回到RemoteViews 的reapply方法public class RemoteViews implements Parcelable, Filter .public void reapply(Context context, View v, OnClickHandler handler) RemoteViews rvToApply = getRemoteViewsToApply(context); . rvToApply.performApply(v, (ViewGroup) v.getParent(), handler); private void performApply(View v, ViewGroup parent, OnClickHandler handler) if (mActions != null) handler = handler = null ? DEFAULT_ON_CLICK_HANDLER : handler; final int count = mAc