了解BroadcastRecever
广播分类:
标准广播(Normal broadcasts):完全异步执行的广播,接收没有先后顺序,效率高,无法被接收器被拦截。
有序广播(Ordered broadcasts) :同步执行的广播,有先后顺序,广播可以被接收器拦截或修改。
接收系统广播:
动态注册监听网络变化:(只能在程序启动后才能接收到广播,程序结束,广播取消)
1.再activity中注册广播并处理接收后的逻辑
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();
//添加要接收的广播类型
intentFilter.addAction("android.net.com.CONNECTIVITY_CHANGE");
//创建广播接收者
networkChangeReceiver = new NetworkChangeReceiver();
//注册广播接收者
registerReceiver(networkChangeReceiver,intentFilter);
} @Override
protected void onDestroy() {
super.onDestroy();
//取消注册
unregisterReceiver(networkChangeReceiver);
} //自定义广播接收者
class NetworkChangeReceiver extends BroadcastReceiver{ @Override
public void onReceive(Context context, Intent intent) {
//收到广播后处理相关逻辑
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();
} }
}
}
2.还要添加访问网络状态的权限:
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/> 静态注册实现开机启动:(程序结束后还能正常接收广播)
1.创建广播接收类:
public class BootCompleteReceiver extends BroadcastReceiver {
public BootCompleteReceiver() {
} @Override
public void onReceive(Context context, Intent intent) { }
}
2.在Manifest中静态注册:
<receiver
android:name=".BootCompleteReceiver"
android:enabled="true"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED"/>
</intent-filter>
</receiver>
enable:是否启用广播接收器
exported:是否允许接收器接收本程序以外的广播
添加监听启动完成广播权限:
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
发送自定义广播:
发送标准广播:
1.首先定义广播接收器
public class MyBroadcastReceiver extends BroadcastReceiver { @Override
public void onReceive(Context context, Intent intent) { }
}
2.在Manifest中注册:
<receiver
android:name=".MyBroadcastReceiver"
android:enabled="true"
android:exported="true">
<intent-filter>
<action android:name="com.example.broadcast.MY_BROADCAST"/>
</intent-filter>
</receiver>
3.发送广播:
public void onClick(View v) {
if(v.getId() == R.id.send){
Intent intent = new Intent("com.example.broadcast.MY_BROADCAST");
sendBroadcast(intent);
}
}
发送有序广播:
1.在注册广播接收器时给intent-filter设置优先级属性,数值越大,优先级越高
<receiver
android:name=".BootCompleteReceiver"
android:enabled="true"
android:exported="true">
<intent-filter
android:priority="100">
<action android:name="android.intent.action.BOOT_COMPLETED"/>
</intent-filter>
</receiver>
2.发送有序广播:
Intent intent = new Intent("com.example.broadcast.MY_BROADCAST");
sendOrderedBroadcast(intent,null);//只需要修改发送方法
3.接收到广播时进行拦截或者修改处理:
public class BootCompleteReceiver extends BroadcastReceiver {
public BootCompleteReceiver() {
} @Override
public void onReceive(Context context, Intent intent) {
abortBroadcast();//拦截广播
setResult(int code,Stirng data, Bundle extras);//修改结果传递给下一个广播
//获取上一个广播传来的数据
getResultCode();
getResultData();
getResultExtras(boolean makeMap);
}
}
4.终结广播(不管是否拦截,都会最终执行)
Intent intent = new Intent("com.example.broadcast.MY_BROADCAST");
sendOrderedBroadcast(intent,null,new BootCompleteReceiver(),new Handler(),0,null,null);
使用本地广播:
本地广播只能在应用内部传递
1.创建广播接收器
class NetworkChangeReceiver extends BroadcastReceiver{ @Override
public void onReceive(Context context, Intent intent) { } }
}
2.获取本地广播管理类:
LocalBroadcastManager localBroadcastManager = LocalBroadcastManager.getInstance(this);
3.注册广播接收器
localBroadcastManager.registerReceiver(networkChangeReceiver,intentFilter);
4.发送广播:
localBroadcastManager.sendBroadcast(intent);
5.注销广播
localBroadcastManager.unregisterReceiver(networkChangeReceiver);
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