（八）Android廣播接收器BroadcastReceiver

標籤：

一、使用Broadcast Reciver 1.右擊java檔案夾，new->other->Broadcast Receiver後會在AndroidManifest.xml檔案中產生一個receiver項

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.shiyanshi.learnbroadcast" >

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver
            android:name=".MyReceiver"
            android:enabled="true"
            android:exported="true" >
        </receiver>
    </application>

</manifest>

2.同時產生了一個MyReceiver 的類，該類中onReceive用於響應sendBroadcast函數發送的訊息

package com.example.shiyanshi.learnbroadcast;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class MyReceiver extends BroadcastReceiver {
    public MyReceiver() {
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        // TODO: This method is called when the BroadcastReceiver is receiving
        // an Intent broadcast.
//        throw new UnsupportedOperationException("Not yet implemented");
        System.out.println("Recv Data:"+intent.getStringExtra("data"));
    }
}

3.調用sendBroadcast函數進行發送訊息，該函數需要一個Intent

package com.example.shiyanshi.learnbroadcast;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;


public class MainActivity extends Activity implements View.OnClickListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViewById(R.id.btnSendMsg).setOnClickListener(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.btnSendMsg:
                Intent intent =new Intent(this,MyReceiver.class);
                intent.putExtra("data","henry");
                sendBroadcast(intent);
                break;
        }
    }
}

二、動態註冊和登出1.刪去AndroidManifest.xml檔案中的receiver時，需要動態註冊和登出，才能發送和接收訊息<receiver
android:name=".MyReceiver"
android:enabled="true"
android:exported="true" >
</receiver>
2.MainActivity更改如下：發送訊息訊息時，Intent要使用隱式Intent（MyReceiver.ACTION為定義的一個常量字串public static final String ACTION="com.example.shiyanshi.learnbroadcast.intent.action.MyReceiver";//前半部分時包名，後半部分時intent的格式，MyReceiver是上述中用於響應sendBroadcast的類），註冊時使用registerReceiver函數，登出時使用unregisterReceiver函數函數原型為：public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter)public void unregisterReceiver(BroadcastReceiver receiver)receiver是我們建立Broadcast時聲稱的用於響應sendBroadcast的MyReceiver類，filter是過濾器，需想起傳遞隱式Intent類似的參數。

 

public class MainActivity extends Activity implements View.OnClickListener {

    private MyReceiver receiver=null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViewById(R.id.btnSendMsg).setOnClickListener(this);
        findViewById(R.id.btnRegister).setOnClickListener(this);
        findViewById(R.id.btnUnregister).setOnClickListener(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.btnSendMsg:
//                Intent intent =new Intent(this,MyReceiver.class);
                //動態註冊和登出時要使用隱式Intent，而不能使用顯示Intent了
                Intent intent=new Intent(MyReceiver.ACTION);
                intent.putExtra("data","henry");
                sendBroadcast(intent);
                break;
            case R.id.btnRegister:
                if (receiver==null){
                    receiver=new MyReceiver();
                    registerReceiver(receiver,new IntentFilter(MyReceiver.ACTION));
                }
                break;
            case R.id.btnUnregister:
                if(receiver!=null){
                    unregisterReceiver(receiver);
                    receiver=null;
                }
                break;
        }
    }
}

三、Broadcast的優先順序當發送資料時，採用隱式Intent的形式（如上），兩個receiver中的action name相同時，二者可以同時接收到資料。預設情況下最後寫的那個receiver所對應的優先順序高，此外可以顯示的在receiver下的Intent-filter中指明優先順序priority，其數值越大，優先順序越高，越先響應資料

 <receiver
        android:name=".MyReceiver1"
        android:enabled="true"
        android:exported="true" >
        <intent-filter android:priority="2">
            <action android:name="com.example.shiyanshi.learnbroadcast.intent.action.MyReceiver"/>
        </intent-filter>
    </receiver>
    <receiver android:name=".MyReceiver"
        android:enabled="true"
        android:exported="true">
        <intent-filter android:priority="1">
            <action android:name="com.example.shiyanshi.learnbroadcast.intent.action.MyReceiver"/>
        </intent-filter>
    </receiver>
</application>

此外，當優先順序高的那個onReceive執行後，可以在其中調用abortBroadcast來終止資料的傳遞，優先順序別低的onReceive便不會執行了.注意：若想使用abortBroadcast函數，發送時需使用sendOrderedBroadcast而非sendBroadcast，否則會彈出錯誤java.lang.RuntimeException: BroadcastReceiver trying to return result during a non-ordered broadcast。

Intent intent=new Intent(MyReceiver.ACTION);
                intent.putExtra("data","henry");
//                sendBroadcast(intent);
                sendOrderedBroadcast(intent,null);

其中sendOrderedBroadcast的第二個參數用來指明許可權，可以為空白

（八）Android廣播接收器BroadcastReceiver