初学Android,BroadcastReceiver之发送接收广播(七十)

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BroadcastReceiver用于监听系统全局广播消息，由于BroadcastReceiver是一种全局的监听器，因此它可以非常方便地实现系统中不同组件之间通信

启动它需要两步

1.创建需要启动的BroadcastReceiver的Intent

2.调用Context的SendBroadcast或sendOrederedBroadcast方法来启动指定的BroadcastReceiver

这其中关键是创建Intent时，要setAction("xxx")，而BroadcastReceiver就要创建它的class="tags" href="/tags/FILTER.html" title=filter>filter，或在代码中指定，或在xml中指定

下面以一个简单例子说明，例子是一个向广播发送消息的程序

发送端主界面代码

class="language-java">package WangLi.Service.Broadcast;

import class="tags" href="/tags/ANDROID.html" title=android>android.app.Activity;
import class="tags" href="/tags/ANDROID.html" title=android>android.content.Intent;
import class="tags" href="/tags/ANDROID.html" title=android>android.os.Bundle;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.View;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.View.OnClickListener;
import class="tags" href="/tags/ANDROID.html" title=android>android.widget.Button;

public class Broadcast extends Activity {
	Button send;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		// 获取界面中的按钮
		send = (Button) findViewById(R.id.send);
		send.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View arg0) {
				// 创建Intent对象
				Intent intent = new Intent();
				// 设置Intent的Action属性
                intent.setAction("WangLi.Test");
                intent.putExtra("msg", "简单的消息");
                //发送广播
                sendBroadcast(intent);
			}
		});
	}
}

接着创建一个BroadcastReceiver监听器

class="language-java">package WangLi.Service.Broadcast;

import class="tags" href="/tags/ANDROID.html" title=android>android.content.BroadcastReceiver;
import class="tags" href="/tags/ANDROID.html" title=android>android.content.Context;
import class="tags" href="/tags/ANDROID.html" title=android>android.content.Intent;
import class="tags" href="/tags/ANDROID.html" title=android>android.widget.Toast;

public class MyReceiver extends BroadcastReceiver {

	@Override
	public void onReceive(Context context, Intent intent) {
		Toast.makeText(
				context,
				"接收到的Intent的Action为:" + intent.getAction() + "\n消息内容是:"
						+ intent.getStringExtra("msg"), 5000).show();
	}

}

向AndroidManifest.xml中配置该receiver，主要是intent class="tags" href="/tags/FILTER.html" title=filter>filter

class="language-html">        <receiver class="tags" href="/tags/ANDROID.html" title=android>android:name="MyReceiver" >
            <intent-class="tags" href="/tags/FILTER.html" title=filter>filter>
                <class="tags" href="/tags/ACTION.html" title=action>action class="tags" href="/tags/ANDROID.html" title=android>android:name="WangLi.Test" />
            </intent-class="tags" href="/tags/FILTER.html" title=filter>filter>
        </receiver>

要注意的是BroadcastReceiver的过期时间为10秒，如果是耗时的操作应放在service中去完成，BroadcastReceiver只适合短时间的计算任务，因为它的生命周期非常短