安卓学习第四篇：Broadcast 使用和Widget 使用

一、实验题目

Broadcast 使用和Widget 使用

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二、要求

• 点击widget可以启动应用，并在widget随机推荐一个食品。

• 点击widget跳转到所推荐食品的详情界面。

• 点击收藏图标，widget相应更新。

• 点击widget跳转到收藏列表。

• 实现方式要求:启动时的widget更新通过静态广播实现，点击收藏图标时的widget更新通过动态广播实现。

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三、实验结果

(1)实验截图

主页外观：

查看今日推荐：

点击今日推荐：

点击收藏：

点击弹出的收藏通知：

widget初始情况如下：

点击widget可以启动应用，并在widget随机推荐一个食品：

点击widget跳转到所推荐食品的详情界面：

点击收藏：

widget相应更新：

点击widget跳转到收藏列表：

(2)实验步骤以及关键代码

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静态广播部分

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• StaticReceiver.java

  定义静态广播接受类，注意channelID的设置和利用PendingIntent.FLAG_UPDATE_CURRENT获取及时更新。

package com.example.a13371.myapplication;
import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.NotificationCompat;
import android.util.Log;
import android.widget.Toast;
import static android.content.Context.NOTIFICATION_SERVICE;
import static java.lang.System.exit;


public class StaticReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {
           Log.i("here", context.toString());
            if (intent.getAction().equals("STATIC")){
                Log.i("where", "aaaaa");
                Bundle bundle = intent.getExtras();
                Collection c = (Collection)bundle.getSerializable("random");
                int importance = NotificationManager.IMPORTANCE_HIGH;
                //将channelID设置为here
                NotificationChannel channel = new NotificationChannel("here", "this", importance);
                channel.setDescription("www");
                NotificationManager notificationManager = context.getSystemService(NotificationManager.class);
                notificationManager.createNotificationChannel(channel);
                Intent mintent = new Intent(context, InfoActivity.class);
                mintent.putExtra("Collection", c);
                mintent.putExtra("flag", true);
                mintent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
                //对intent进行更新，这里一定不要设错了
                PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, mintent, PendingIntent.FLAG_UPDATE_CURRENT);
                //这里要写上对应的channelID
                NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(context, "here")
                        .setSmallIcon(R.mipmap.empty_star)
                        .setContentTitle("今日推荐")
                        .setContentText(c.getName())
                        .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                        // Set the intent that will fire when the user taps the notification
                        .setContentIntent(pendingIntent)
                        .setAutoCancel(true);
                Notification notify = mBuilder.build();
                notificationManager.notify(1,notify);

            }
        }
    }

• AndroidManifest.xml

  在此处对静态广播进行注册，并更改launchMode为"singleInstance"。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.a13371.myapplication">

    <application
        android:allowBackup="false"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.AppCompat.Light.NoActionBar">
        <activity android:name=".MainActivity"
            android:launchMode="singleInstance">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name="com.example.a13371.myapplication.InfoActivity"/>

        <receiver android:name=".StaticReceiver">
            <intent-filter>
                <action android:name="STATIC" />
            </intent-filter>
        </receiver>

    </application>

</manifest>

• MainActivity.java

  在此处产生随机推荐并发出静态广播。

  //产生随机推荐
        Random random = new Random();
        int r = random.nextInt(clist.size()); //返回一个0到n-1的整数
        Bundle bundle = new Bundle();
        Intent intentBroadcast = new Intent("STATIC"); //定义Intent
        bundle.putSerializable("random", clist.get(r));
        ComponentName componentName = new ComponentName(getPackageName(),"com.example.a13371.myapplication.StaticReceiver");
        intentBroadcast.setComponent(componentName);
        intentBroadcast.putExtras(bundle);
        sendBroadcast(intentBroadcast);

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动态广播部分

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• DynamicReceiver.java

  定义动态广播接受类，注意事项与静态一致。

package com.example.a13371.myapplication;
import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.NotificationCompat;
import android.util.Log;

public class DynamicReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Log.i("DDDD", context.toString());
        if (intent.getAction().equals("DYNAMIC")) {    //动作检测

            int importance = NotificationManager.IMPORTANCE_HIGH;
            NotificationChannel channel = new NotificationChannel("there", "this", importance);
            channel.setDescription("hhh");
            NotificationManager notificationManager = (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
            notificationManager.createNotificationChannel(channel);
            Intent mIntent = new Intent(context, MainActivity.class);
            mIntent.putExtra("like", "this");
            //对intent进行更新


            Bundle bundle = intent.getExtras();
            NotificationCompat.Builder builder = new NotificationCompat.Builder(context, "there");
            builder.setContentTitle("已收藏")
                    .setContentText(bundle.getString("name"))
                    .setSmallIcon(R.mipmap.empty_star)
                    .setWhen(System.currentTimeMillis())
                    .setTicker("您有一条新消息");


            PendingIntent mPendingIntent = PendingIntent.getActivity(context, 0, mIntent, PendingIntent.FLAG_UPDATE_CURRENT);
            builder.setContentIntent(mPendingIntent);
            //绑定Notification，发送通知请求
            Notification notify = builder.build();
            notificationManager.notify(1, notify);
            Log.i("DDDD", "finished");
        }
    }

}

• InfoActivity.java

  在点击收藏事件里对动态广播进行注册，activity结束后进行撤销。

Bundle bundle = new Bundle();
bundle.putString("name", sname);
Intent intent = new Intent("DYNAMIC");
intent.putExtras(bundle);
sendBroadcast(intent);


                
@Override
protected void onDestroy() {
   super.onDestroy();
   unregisterReceiver(dynamicReceiver);
 }
                

• MainActivity.java

  在此处接收动态广播，并调整可见状态。

    //调整可见状态
    @Override
    protected void onNewIntent(Intent intent) {
        Log.i("goout", "received");
        super.onNewIntent(intent);
        setIntent(intent);
        Bundle extras = intent.getExtras();
        if(extras != null) {
            if(extras.getString("like").equals("this")) {
                Log.i("why", extras.getString("like"));
                Favorite.setVisibility(View.VISIBLE);
                RView.setVisibility(View.INVISIBLE);
                btn.setImageDrawable(getResources().getDrawable(R.mipmap.favorate));
                click = !click;
            }
        }
    }

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EventBus部分

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• MessageEvent.java

package com.example.a13371.myapplication;

public class MessageEvent {
    private String name;
    private String circle;

    public MessageEvent(String name, String circle) {
        super();
        this.name = name;
        this.circle = circle;
    }

    public String getName() {
        return name;
    }

    public String getCircle() {
        return circle;
    }
}

• InfoActivity.java

  在点击收藏事件里发送EventBus。

 EventBus.getDefault().post(new MessageEvent(sname, scircle));             

• MainActivity.java

  在此处注册接收和退出EventBus

    //注册
   EventBus.getDefault().register(this);
    
     
     //收到消息
    @Subscribe(threadMode = ThreadMode.MAIN)
    public void onMessageEvent(MessageEvent event) {
        Map<String, Object> k = new LinkedHashMap<>();
        k.put("cycle", event.getCircle());
        k.put("name", event.getName());
        this.favoritethings.add(k);
        simpleAdapter1.notifyDataSetChanged();
    }
    
    
    
    //退出
    @Override
    protected void onDestroy() {
        super.onDestroy();
        EventBus.getDefault().unregister(this);
    }

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widget部分

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• NewAppWidget.java

  定义widget类，在其中完成初始化和更新方法。

package com.example.a13371.myapplication;
import android.app.PendingIntent;
import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProvider;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.widget.RemoteViews;

/**
 * Implementation of App Widget functionality.
 */
public class NewAppWidget 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.new_app_widget);
        views.setTextViewText(R.id.appwidget_text, widgetText);

        // Instruct the widget manager to update the widget
        appWidgetManager.updateAppWidget(appWidgetId, views);
    }

    @Override
    public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
        // There may be multiple widgets active, so update all of them
        RemoteViews updateView = new RemoteViews(context.getPackageName(), R.layout.new_app_widget);//实例化RemoteView,其对应相应的Widget布局
        Intent i = new Intent(context, MainActivity.class);
        PendingIntent pi = PendingIntent.getActivity(context, 0, i, PendingIntent.FLAG_UPDATE_CURRENT);
        updateView.setOnClickPendingIntent(R.id.wclick, pi); //设置点击事件
        ComponentName me = new ComponentName(context, NewAppWidget.class);
        appWidgetManager.updateAppWidget(me, updateView);
    }

    @Override
    public void onEnabled(Context context) {
        // Enter relevant functionality for when the first widget is created
    }

    @Override
    public void onDisabled(Context context) {
        // Enter relevant functionality for when the last widget is disabled
    }

    @Override
    public void onReceive(Context context, Intent intent ){
        super.onReceive(context, intent);
        if(intent.getAction().equals("STATIC")){
            Log.i("hihihi", "onReceive: ");
            Bundle bundle = intent.getExtras();
            Collection c = (Collection)bundle.getSerializable("random");
            Intent mintent = new Intent(context, InfoActivity.class);
            mintent.putExtra("Collection", c);
            RemoteViews updateViews = new RemoteViews(context.getPackageName(), R.layout.new_app_widget);
            PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, mintent, PendingIntent.FLAG_UPDATE_CURRENT);
            updateViews.setOnClickPendingIntent(R.id.wclick, pendingIntent);//给RemoteView上的Button设置按钮事件
            updateViews.setTextViewText(R.id.appwidget_text, "今日推荐 "+c.getName());
            ComponentName me = new ComponentName(context, NewAppWidget.class);
            AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);
            appWidgetManager.updateAppWidget(me, updateViews);
        }
    }

}

• AndroidManifest.xml

  新增注册静态广播。

        <receiver android:name=".NewAppWidget">
            <intent-filter>
                <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
                <action android:name="STATIC" />
            </intent-filter>

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

• new_app_widget.xml

  定义widget的外观。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/wclick"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="@dimen/widget_margin">

    <ImageView
        android:id="@+id/appstar"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:layout_alignParentTop="true"
        android:src="@mipmap/full_star" />

    <TextView
        android:id="@+id/appwidget_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:contentDescription="@string/appwidget_text"
        android:text="@string/appwidget_text"
        android:textColor="@color/white"
        android:textSize="15sp"
        android:textStyle="bold|italic"
        android:layout_toRightOf="@+id/appstar"
        android:layout_alignBaseline= "@+id/appstar"
        android:layout_marginTop="17dp"
        android:layout_marginLeft="3dp"
        android:layout_alignParentTop="true"/>

</RelativeLayout>

• new_app_widget_info.xml

  定义widget的基本属性。

<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
    android:initialKeyguardLayout="@layout/new_app_widget"
    android:initialLayout="@layout/new_app_widget"
    android:minWidth="300dp"
    android:minHeight="50dp"
    android:previewImage="@mipmap/full_star"
    android:resizeMode="horizontal|vertical"
    android:updatePeriodMillis="86400000"
    android:widgetCategory="home_screen|keyguard"></appwidget-provider>

• MainActivity.java

  在此处将随机推荐写入onRestart方法。

     @Override
    protected void onRestart() {
        super.onRestart();
        //        产生随机推荐
        if (flag && !clist.isEmpty()) {
            Random random = new Random();
            int r = random.nextInt(clist.size()); //返回一个0到n-1的整数
            Bundle bundle = new Bundle();
            Intent intentBroadcast = new Intent("STATIC"); //定义Intent
            bundle.putSerializable("random", clist.get(r));
            ComponentName componentName = new ComponentName(getPackageName(),"com.example.a13371.myapplication.StaticReceiver");
            intentBroadcast.setComponent(componentName);
            intentBroadcast.putExtras(bundle);
            sendBroadcast(intentBroadcast);
            ComponentName wcomponentName = new ComponentName(getPackageName(),"com.example.a13371.myapplication.NewAppWidget");
            intentBroadcast.setComponent(wcomponentName);
            sendBroadcast(intentBroadcast);
            flag = !flag;
        }
    }

• DynamicReceiver.java

  增添对widget接受动态消息的部分。

            Intent mintent = new Intent(context, MainActivity.class);
            mintent.putExtra("like", "this");
            RemoteViews updateViews = new RemoteViews(context.getPackageName(), R.layout.new_app_widget);
            PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, mintent, PendingIntent.FLAG_UPDATE_CURRENT);
            updateViews.setOnClickPendingIntent(R.id.wclick, pendingIntent);//给RemoteView上的Button设置按钮事件
            updateViews.setTextViewText(R.id.appwidget_text, "已收藏 "+ bundle.getString("name"));
            ComponentName me = new ComponentName(context, NewAppWidget.class);
            AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);
            appWidgetManager.updateAppWidget(me, updateViews);

(3)实验遇到的困难以及解决思路

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• 不知道如何获取bitmap。

参照这篇博客解决。

 BitmapDrawable drawable = (BitmapDrawable)db;
 Bitmap bitmap = drawable.getBitmap();
 Bitmap bt = BitmapFactory.decodeResource(context.getResources(),
 R.mipmap.empty_star);

• Android编译时提示“App is not indexable by Google Search; consider adding at least one Activity with an ACTION-VIEW”

参照这篇博客解决。

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.a13371.myapplication"
        minSdkVersion 26
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    lintOptions {
        disable 'GoogleAppIndexingWarning'
    }
    productFlavors {
    }
}

• 提示"On SDK version 23 and up, your app data will be automatically backed up and restored on app install."。

参照这篇博客解决

configurations.all {
    resolutionStrategy.eachDependency { DependencyResolveDetails details ->
        def requested = details.requested
        if (requested.group == 'com.android.support') {
            if (!requested.name.startsWith("multidex")) {
                details.useVersion '28.0.0'
            }
        }
    }
}

• 不知道如何查看断点。

参照这篇博客解决

• 修改版本时com.android.support冲突的解决办法。

参照这篇博客解决

• 静态广播无法被接收。

参照这篇博客解决

ComponentName componentName = new ComponentName(getPackageName(),"com.example.a13371.myapplication.StaticReceiver");
intentBroadcast.setComponent(componentName);

• 不知道android studio 有的代码加了删除线是怎么回事。

参照这篇博客解决

——说明是decrepted代码，这种代码在以前的版本适用，现在有新的代码来替代旧的。但是IDE依旧能识别所以能继续运行

• Android发通知 PendingIntent 中Intent 内容没有更新。

参照这篇博客解决

PendingIntent contentIntentBegin = PendingIntent.getActivity( notificationContext, 0, inStart, PendingIntent.FLAG_UPDATE_CURRENT);

• Android的onNewIntent方法不及时更新。

参照这篇博客解决

• 对Android生命周期有些不清楚。

参照这篇博客解决

这张图真是很优秀了：

• Android的onRestart方法调用时机。

参照这篇博客解决

（1）按下home键之后，然后切换回来，会调用onRestart()。

（2）从本Activity跳转到另一个Activity之后，按back键返回原来Activity，会调用onRestart()；

（3）从本Activity切换到其他的应用，然后再从其他应用切换回来，会调用onRestart()；

四、实验思考及感想

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在这次实验当中，我最大的收获是学会了使用log来灵活的调试，以确定程序目前的运行状态，和在不同状态时各种变量的值，这让我能更快地找出问题所在，也更能深刻地理解Android中各个activity生命周期的演变。

附上一张调试时的妖艳截图：