Notification使用详解之二：可更新进度的通知

注意，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。

然后再来看一下MainActivity.java的代码：

package com.scott.notification;

import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.RemoteViews;

public class MainActivity extends Activity {

	private static final int NOTIFY_ID = 0;

	private boolean cancelled;

	private NotificationManager mNotificationManager;
	private Notification mNotification;

	private Context mContext = 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 = mNotification.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
					mNotification.flags = Notification.FLAG_AUTO_CANCEL;
					mNotification.contentView = null;
					Intent intent = new Intent(mContext, FileMgrActivity.class);
					PendingIntent contentIntent = PendingIntent.getActivity(mContext, 0, intent, 0);
					mNotification.setLatestEventInfo(mContext, "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
				mNotificationManager.notify(NOTIFY_ID, mNotification);
				break;
			case 0:
				// 取消通知
				mNotificationManager.cancel(NOTIFY_ID);
				break;
			}
		};
	};

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
	}

	public void download(View view) {
		mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

		int icon = R.drawable.down;
		CharSequence tickerText = "开始下载";
		long when = System.currentTimeMillis();
		mNotification = new Notification(icon, tickerText, when);

		// 放置在"正在运行"栏目中
		mNotification.flags = Notification.FLAG_ONGOING_EVENT;

		RemoteViews contentView = new RemoteViews(mContext.getPackageName(), R.layout.download_notification_layout);
		contentView.setTextViewText(R.id.fileName, "AngryBird.apk");
		// 指定个性化视图
		mNotification.contentView = contentView;

		// intent为null,表示点击通知时不跳转
		PendingIntent contentIntent = PendingIntent.getActivity(mContext, 0, null, 0);
		// 指定内容意图
		mNotification.contentIntent = contentIntent;

		mNotificationManager.notify(NOTIFY_ID, mNotification);

		new Thread() {
			public void run() {
				startDownload();
			};
		}.start();
	}

	public void cancel(View view) {
		cancelled = true;
	}

	private void startDownload() {
		cancelled = false;
		int rate = 0;
		while (!cancelled && 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 (cancelled) {
			Message msg = handler.obtainMessage();
			msg.what = 0;
			handler.sendMessage(msg);
		}
	}
}

值得注意的是，在控制下载线程时使用了cancelled这个boolean值标志变量，对于线程的控制更好一些，不建议使用Thread.interrupt()去中断一个线程。另外，对于更新通知的UI界面时，要记住调用NotificationManager.notify(int id, Notification notification)方法通知一下，否则即使设置了新值，也不会起作用的。

程序中用到的带进度的通知布局/res/layout/download_notification_layout.xml布局文件代码如下：