BroadcastReceiver

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BroadcastReceiver:广播接收者，接收发送过来的广播，本质是全局监听器。广播作为Android一种通信方式，用途十分广泛。例如：开机启动后会接收到启动服务的广播，电量变化时会接收电量低及时保存的广播提示，网络变化会接收及时提示和保存的提示，检测SD状态广播等等。
BroadcastReceiver的生命周期：
实现BroadcastReceiver的实例非常简单，继承BroadcastReceiver会调用onReceive()，所有的操作直接在onReceive()中运行。执行完之后，BroadcastReceiver直接销毁。该方法直接运行在UI线程中，大概只有10s左右，所以不可做耗时操作。
如何注册：
首先自定义一个BroadcastReceiver对象，继承BroadcastReceiver

public class MyReceiver extends BroadcastReceiver {    private static final String Tag = "Myreceive";    @Override    public void onReceive(Context context, Intent intent) {        String msg = intent.getStringExtra("msg");         Log.i(Tag,"Myreceive:"+ msg);    }}

注册：
1.静态注册：在AndroidManifest.xml中实现

<receiver android:name=".MyReceiver">    <intent-filter>       <action android:name="MY_BROADCAST"/><!-- 隐式发送，用来匹配Intent-->       <category android:name="android.intent.category.DEFAULT"/>    </intent-filter></receiver>

补充（隐式跳转）：
1.一个Intent可以有多个category目录，但至少会有一个默认的；
2.只有Intent的所有category都匹配上了，Activity才能接受这个Intent。
所以为什么要加category 这个默认方式了。
MianActivity代码：

 protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button bt_send = (Button) findViewById(R.id.bt_send);        bt_send.setOnClickListener(new View.OnClickListener() {        @Override        public void onClick(View v) {           Intent intent = new  Intent("android.intent.action.MY_BROADCAST");//在配置文件中的action目录做的配置                                                intent.putExtra("msg","hello World");                                      sendBroadcast(intent);                      }               }        );    }

添加了一个发送按钮，用来发送广播
结果：
这里写图片描述
2.动态注册

MyReceiver myReceiver = new MyReceiver();IntentFilter intentFilter = new IntentFilter();      intentFilter.addAction("android.intent.action.MY_BROADCAST");registerReceiver(myReceiver,intentFilter);//动态注册

结果：
这里写图片描述
动态注册在程序关闭时是收不到广播的，但是静态可以。

根据广播的发送方式可以分为：
1.Normal Broadcast普通广播
2.System Broadcast系统广播
3.Ordered Broadcast有序广播
4.Local BroadcastApp内部广播
5.Sticky Broadcast粘性广播（5.0不在推荐）

1.普通广播：
建立了三个自定义广播类
MyReceiver

public class MyReceiver extends BroadcastReceiver {    private static final String Tag = "Myreceive";    @Override    public void onReceive(Context context, Intent intent) {        String msg = intent.getStringExtra("msg");        Log.i(Tag, "Myreceive:" + msg);    }}

FirstReceiver

public class FirstReceiver extends BroadcastReceiver {    private static final String Tag = "FirstReceiver";    @Override    public void onReceive(Context context, Intent intent) {        String msg = intent.getStringExtra("msg");        Log.i(Tag, "FirstReceiver:" + msg);    }}

SecondReceiver

public class SecondReceiver extends BroadcastReceiver {    private static final String Tag = "SecondReceiver";    @Override    public void onReceive(Context context, Intent intent) {        String msg = intent.getStringExtra("msg");        Log.i(Tag, "SecondReceiver:" + msg);    }}

MainActivity：

public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button bt_send = (Button) findViewById(R.id.bt_send);        bt_send.setOnClickListener(new View.OnClickListener() {       @Override       public void onClick(View v) {       Intent intent = new   Intent("android.intent.action.MY_BROADCAST");       intent.putExtra("msg","hello World");       sendBroadcast(intent);                }            }        );    }}

在配置文件中添加相应的配置
结果：

04-06 08:01:34.308 30288-30288/com.appress.gerber.broadcastreceiver I/Myreceive: **Myreceive:hello World**04-06 08:01:34.308 30288-30288/com.appress.gerber.broadcastreceiver I/FirstReceiver: **FirstReceiver:hello World**04-06 08:01:34.308 30288-30288/com.appress.gerber.broadcastreceiver I/SecondReceiver: **SecondReceiver:hello World**

都接收到了消息。

有序广播：
使用sendOrderedBroadcast()方法，优先级-1000到1000
在配置文件中配置优先级

    <receiver android:name=".MyReceiver">        <intent-filter android:priority="10"><!--优先级10-->            <action android:name="android.intent.action.MY_BROADCAST"/><!-- 隐式发送，用来匹配Intent-->            <category android:name="android.intent.category.DEFAULT"/>        </intent-filter>    </receiver>        <receiver android:name=".FirstReceiver">            <intent-filter android:priority="80"><!--优先级80-->                <action android:name="android.intent.action.MY_BROADCAST"/><!-- 隐式发送，用来匹配Intent-->                <category android:name="android.intent.category.DEFAULT"/>            </intent-filter>        </receiver>        <receiver android:name=".SecondReceiver">            <intent-filter android:priority="-20"><!--优先级-20-->                <action android:name="android.intent.action.MY_BROADCAST"/><!-- 隐式发送，用来匹配Intent-->                <category android:name="android.intent.category.DEFAULT"/>            </intent-filter>        </receiver>

MainActivity：没有做设置权限，直接null，如果设置权限只能接收相同权限的广播。

 sendOrderedBroadcast(intent,null);

结果：优先级FirstReceiver，Myreceive，SecondReceiver

04-06 08:18:36.716 14590-14590/com.appress.gerber.broadcastreceiver I/FirstReceiver: **FirstReceiver:hello World**04-06 08:18:36.716 14590-14590/com.appress.gerber.broadcastreceiver I/Myreceive: **Myreceive:hello World**04-06 08:18:36.716 14590-14590/com.appress.gerber.broadcastreceiver I/SecondReceiver: **SecondReceiver:hello World**

Local Broadcast：App内部广播，说明广播可以跨进程之间通信。（自己不怎么了解）
System Broadcast：Android系统内置了多个系统广播，只要涉及到基本操作的基本上都带有广播

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