1，

掌握Widget的用：

Widget的用途，能够添加到手机桌面的程序

2，

Widget的特点和用法步骤：

特点：快捷，方便，个性化，可自定义功能，可及时控制更新Widget显示内容

3，

 用法步骤流程图

1. 绘制Widget布局
2. 配置Widget的基本属性
3. 定义AppWidgetProvider
4. 提供Configuration Activity

4,

Android Widget实现一个基础的时钟功能

效果：

• 可以自动更新时间
• 可以添加和删除时钟Widget

5，

完整代码：

package com.example.widget;import android.appwidget.AppWidgetManager;import android.appwidget.AppWidgetProvider;import android.content.Context;import android.content.Intent;import android.widget.RemoteViews;/** * 类似广播，是桌面小组件Widget的Provider */public class widget extends AppWidgetProvider {    static void updateAppWidget(Context context, AppWidgetManager appWidgetManager,                                int appWidgetId) {        CharSequence widgetText = context.getString(R.string.appwidget_text);        // Construct the RemoteViews object        RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.widget);        views.setTextViewText(R.id.tv, widgetText);        // Instruct the widget manager to update the widget        appWidgetManager.updateAppWidget(appWidgetId, views);    }    //刷新widget的时候执行，remoteView和AppWidgetManager    @Override    public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {        // There may be multiple widgets active, so update all of them        for (int appWidgetId : appWidgetIds) {            updateAppWidget(context, appWidgetManager, appWidgetId);        }    }    //第一个widget添加到屏幕上执行    @Override    public void onEnabled(Context context) {        // Enter relevant functionality for when the first widget is created        super.onEnabled(context);        //启动Service        context.startService(new Intent(context, TimerService.class));    }    //最后一个widget被从屏幕移除执行    @Override    public void onDisabled(Context context) {        // Enter relevant functionality for when the last widget is disabled        super.onDisabled(context);        context.stopService(new Intent(context, TimerService.class));    }    //Widget被从屏幕移除    @Override    public void onDeleted(Context context, int[] appWidgetIds) {        super.onDeleted(context, appWidgetIds);    }    //这个方法一般不会重写，无论操作中间（上面）的哪些方法，都会执行onReceive    @Override    public void onReceive(Context context, Intent intent) {        super.onReceive(context, intent);    }}

　service:

package com.example.widget;import android.app.Service;import android.appwidget.AppWidgetManager;import android.content.ComponentName;import android.content.Intent;import android.os.IBinder;import android.widget.RemoteViews;import androidx.annotation.Nullable;import java.text.SimpleDateFormat;import java.util.Date;import java.util.Timer;import java.util.TimerTask;public class TimerService extends Service {    //java.util.Timer下的定时器    private Timer timer;    private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");    @Nullable    @Override    public IBinder onBind(Intent intent) {        return null;    }    @Override    public void onCreate() {        super.onCreate();        timer = new Timer();        timer.schedule(new TimerTask() {            @Override            public void run() {                updateViews();            }        }, 0, 1000);    }    private void updateViews() {        String time = sdf.format(new Date());        RemoteViews rv = new RemoteViews(getPackageName(), R.layout.widget);        rv.setTextViewText(R.id.tv, "黄朝阳666 ： " + time);        AppWidgetManager manager = AppWidgetManager.getInstance(getApplicationContext());        ComponentName cn = new ComponentName(getApplicationContext(), widget.class);        manager.updateAppWidget(cn, rv);    }    @Override    public void onDestroy() {        super.onDestroy();        timer = null;    }}

6，

添加和删除天气Widget:

 

7，

8，