Android--广播

最新推荐文章于 2024-05-08 11:46:20 发布

原创最新推荐文章于 2024-05-08 11:46:20 发布 · 302 阅读

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1. 安卓提供了一整套API，允许应用程序自由地发送和接受广播

2. 发送广播：Intent 接收广播：BroadcastReceiver

3.
标准广播：异步广播，同时接收
有序广播：同步广播，先后接收，可截获

4. 注册广播：动态注册（在代码中），静态注册（在AndroidManifest.xml中）

5. 创建一个广播接收器，新建一个类，继承自BroadcastReceiver,并重写onReceive()

6. 动态注册：
作用：监听网络变化

package com.example.zzz.broadcast;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private IntentFilter intentFilter;
    private NetworkChangeReceiver networkChangeReceiver;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        intentFilter=new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        networkChangeReceiver=new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver,intentFilter);

    }

    protected void onDestroy(){
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }

    class NetworkChangeReceiver extends BroadcastReceiver {
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
            if (networkInfo != null && networkInfo.isAvailable())
                Toast.makeText(context, "network is available", Toast.LENGTH_SHORT).show();
            else
                Toast.makeText(context, "network is unavailable", Toast.LENGTH_SHORT).show();
        }
    }
}

每当网络变化时，onReceive()就会执行
intentFilter需要添加一个实例(android.net.conn.CONNECTIVITY_CHANGE)，我们广播接收器想要接受怎样的广播，直接addAction就可以了，然后将intentFilter和networkChangeReceiver注册。
记得一定要在onDestroy()取消注册

然后要在AndroidManifest.xml中加入

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

7.静态注册
新建一个类

public class BootCompleteReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"开机成功",Toast.LENGTH_LONG).show();
    }
}

然后在AndroidManifest.xml中加入

<application
    android:theme="@style/AppTheme">
    <receiver android:name=".BootCompleteReceiver">
        <intent-filter>
            <action android:name="android.intent.action.BOOT_COMPLETED"/>
        </intent-filter>
    </receiver>
</application>

不要再onReceive()中加入过多逻辑，因为广播不允许开启线程

8. 发送标准广播
我们通过一个按钮来发送广播，广播接收器接收到广播后执行具体操作。

首先建立布局文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<Button
android:id="@+id/button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Send Broadcast"
/>
</LinearLayout>

然后创建一个自己的广播

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent intent = new Intent(
                        "com.example.broadcasttest.MY_BROADCAST");
                sendBroadcast(intent);
            }
        });
    }

再新建一个广播接收器来接收我们发送的广播

public class MyBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "received", Toast.LENGTH_SHORT).show();
    }
}

最后注册广播接收器

 <receiver android:name=".MyBroadcastReceiver" >
            <intent-filter>
                <action android:name="com.example.mybroadcast. MY_BROADCAST" />
            </intent-filter>
        </receiver>