第五十讲：Android之Nothfication（三）

勤能补拙是良训，一分辛劳一分才。

本讲内容：通知 Notification 和 通知管理器 NotificationManager

我们通过一个例子实现一个可更新进度的通知，代码的讲解都写在注释里了

下面是res/layout/activity_main.xml 布局文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.text1.MainActivity$PlaceholderFragment" >
	<Button
	    android:id="@+id/download"
	    android:layout_width="match_parent"
	    android:layout_height="wrap_content"
	    android:text="download"
	    android:onClick="download"/>
	<Button
	    android:id="@+id/cancel"
	    android:layout_width="match_parent"
	    android:layout_height="wrap_content"
	    android:text="cancel"
	    android:onClick="cancel"/>
	<!-- 为了使示例中的Java代码看起来结构更加清晰，我们将按钮的点击事件都定义在布局文件中。 -->
</LinearLayout>

下面是带进度的通知布局/res/layout/download_notification_layout.xml自定义布局文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="3dp">
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="3dp"
        android:src="@drawable/ic_launcher"/>
    <TextView
        android:id="@+id/fileName"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_toRightOf="@id/imageView"
        android:layout_alignBottom="@id/imageView"
        android:gravity="center_vertical"
        android:textColor="#0f0"/>
    <TextView
        android:id="@+id/rate"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/imageView"
        android:layout_alignRight="@id/imageView"
        android:gravity="center"
        android:text="0%"
        android:textColor="#0f0"/>
    <ProgressBar
        android:id="@+id/progress"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/fileName"
        android:layout_alignLeft="@id/fileName"
        android:max="100"
        android:progress="0"/>
</RelativeLayout>

下面是MainActivity.java主界面文件：

public class MainActivity extends Activity {
	private Notification notification;
	private NotificationManager notificationManager;
	private static final int NOTIFY_ID=0;
	private boolean flag;
	private Context context=this;

	private Handler handler=new Handler(){
		public void handleMessage(android.os.Message msg) {
			switch (msg.what) {
			case 1:
				int rate=msg.arg1;
				if(rate<100){
					 // 更新进度
                    RemoteViews contentView = notification.contentView;
                    contentView.setTextViewText(R.id.rate, rate + "%");
                    contentView.setProgressBar(R.id.progress, 100, rate, false);
				}else{
					// 下载完毕后变换通知形式
                    notification.flags = Notification.FLAG_AUTO_CANCEL;
                    notification.contentView = null;
                    Intent intent = new Intent(context, NotifyActivity.class);
                    PendingIntent contentIntent = PendingIntent.getActivity(context, 0, intent, 0);
                    notification.setLatestEventInfo(context, "下载完成", "文件已下载完毕", contentIntent);
				}
				 // 最后别忘了通知一下,否则不会更新
                notificationManager.notify(NOTIFY_ID, notification);
				break;

			case 0:
				 // 取消通知
                notificationManager.cancel(NOTIFY_ID);
                break;
			}
		};
	};
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
	}
	public void download(View view){
		notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);  

        int icon = R.drawable.ic_launcher;
        CharSequence tickerText = "开始下载";
        long when = System.currentTimeMillis();
        notification = new Notification(icon, tickerText, when);
     // 放置在"正在运行"栏目中
        notification.flags = Notification.FLAG_ONGOING_EVENT;  

        //点击通知时不跳转
        PendingIntent contentIntent = PendingIntent.getActivity(context, 0, getIntent(), 0); 

        RemoteViews contentView = new RemoteViews(context.getPackageName(), R.layout.download_notification_layout);
        contentView.setTextViewText(R.id.fileName, "AngryBird.apk");
        // 指定个性化视图
        notification.contentView = contentView;
        // 指定内容意图
       notification.contentIntent = contentIntent; 

        notificationManager.notify(NOTIFY_ID, notification);  

        new Thread() {
            public void run() {
                startDownload();
            };
        }.start();
	}
	 public void cancel(View view) {
	        flag = true; // 在控制下载线程时使用了flag这个boolean值标志变量，对于线程的控制更好一些
	    }
	 private void startDownload() {
	        flag = false;
	        int rate = 0;
	        while (!flag && rate < 100) {
	            try {
	                // 模拟下载进度
	                Thread.sleep(500);
	                rate = rate + 5;
	            } catch (InterruptedException e) {
	                e.printStackTrace();
	            }
	            Message msg = handler.obtainMessage();
	            msg.what = 1;
	            msg.arg1 = rate;
	            handler.sendMessage(msg);
	        }
	        if (flag) {
	            Message msg = handler.obtainMessage();
	            msg.what = 0;
	            handler.sendMessage(msg);
	        }
	    }
}

上面涉及到线程和handler类，后面章节我们会深入讲解

下面是运行结果：

本讲就到这里，Take your time and enjoy it