编写android的widget

以前对这个东西很感兴趣，因为确实方便，如今有时间了来做一个例子

首先要定义一个layout(widgetview.xml)和一个配置文件(widgetconfig.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/tv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="时间显示" />

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
    android:initialLayout="@layout/widget"
    android:minHeight="40dp"
    android:minWidth="100dp"
    android:updatePeriodMillis="864000" >

</appwidget-provider>

然后再实现一个widgetProvider

package com.example.widgettest;


import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProvider;
import android.content.Context;
import android.content.Intent;

public class WidgetProvider extends AppWidgetProvider {
    @Override
    public void onDeleted(Context context, int[] appWidgetIds) {
        super.onDeleted(context, appWidgetIds);
        // widget被移除
    }

    @Override
    public void onDisabled(Context context) {
        super.onDisabled(context);
        // 最后一个被移除
        context.stopService(new Intent(context, TimerService.class));
    }

    @Override
    public void onEnabled(Context context) {
        super.onEnabled(context);
        // widget添加到屏幕上
        context.startService(new Intent(context, TimerService.class));
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        super.onReceive(context, intent);
    }

    @Override
    public void onUpdate(Context context, AppWidgetManager appWidgetManager,
            int[] appWidgetIds) {
        super.onUpdate(context, appWidgetManager, appWidgetIds);
        // 刷新widget
    }
}

通过一个service对provider进行刷新

package com.example.widgettest;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

import android.app.Service;
import android.appwidget.AppWidgetManager;
import android.content.ComponentName;
import android.content.Intent;
import android.os.IBinder;
import android.widget.RemoteViews;

public class TimerService extends Service {
    private Timer timer;
    private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void onCreate() {
        // TODO Auto-generated method stub
        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, time);
        AppWidgetManager manager = AppWidgetManager
                .getInstance(getApplicationContext());
        ComponentName cn = new ComponentName(getApplicationContext(),
                WidgetProvider.class);
        manager.updateAppWidget(cn, rv);
    }

    @Override
    public void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        timer = null;
    }

}

最后要注册AndroidManifest文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.widgettest"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="23" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <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>

        <service android:name="com.example.widgettest.TimerService" >
        </service>

        <receiver android:name="com.example.widgettest.WidgetProvider" >
            <intent-filter>
                <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
            </intent-filter>

            <meta-data
                android:name="android.appwidget.provider"
                android:resource="@xml/widgetconfig" />
        </receiver>
    </application>

</manifest>