android中broadcastreceiver的用法-代码中注册

界面如下：

   

问题1：点击“解绑广播接收器“后再次点击”解绑广播接收器“后，程序崩溃，log信息如下：

08-04 05:04:35.420: E/AndroidRuntime(5521): FATAL EXCEPTION: main
08-04 05:04:35.420: E/AndroidRuntime(5521): java.lang.IllegalArgumentException: Receiver not registered:com.jinhoward.broadcast.receiver.SecondReceiver@40cfec98
08-04 05:04:35.420: E/AndroidRuntime(5521):     at android.app.LoadedApk.forgetReceiverDispatcher(LoadedApk.java:657)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at android.app.ContextImpl.unregisterReceiver(ContextImpl.java:1339)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at android.content.ContextWrapper.unregisterReceiver(ContextWrapper.java:445)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at com.jinhoward.broadcast.activity.MainActivity$3.onClick(MainActivity.java:62)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at android.view.View.performClick(View.java:4204)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at android.view.View$PerformClick.run(View.java:17355)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at android.os.Handler.handleCallback(Handler.java:725)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at android.os.Handler.dispatchMessage(Handler.java:92)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at android.os.Looper.loop(Looper.java:137)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at android.app.ActivityThread.main(ActivityThread.java:5041)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at java.lang.reflect.Method.invokeNative(Native Method)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at java.lang.reflect.Method.invoke(Method.java:511)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-04 05:04:35.420: E/AndroidRuntime(5521):     at dalvik.system.NativeStart.main(Native Method)

后来排查代码百度找到问题答案，通过一个布尔变量来判断广播接收器是否已经注册。

package com.jinhoward.broadcast.activity;import android.app.Activity;import android.content.Intent;import android.content.IntentFilter;import android.os.Bundle;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.Toast;import com.jinhoward.broadcast.receiver.SecondReceiver;public class MainActivity extends Activity {protected static final String ACTION = "com.jinhoward.broadcast.ACTION";private Button btnBroadcast;private Button registerReceiver;private Button unregisterReceiver;private SecondReceiver receiver;private Boolean registerBoolean;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);btnBroadcast = (Button) findViewById(R.id.btnBroadcast);btnBroadcast.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {Intent intent = new Intent();intent.setAction(ACTION);sendBroadcast(intent);}});registerReceiver = (Button) findViewById(R.id.btnregisterReceiver);registerReceiver.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {receiver = new SecondReceiver();IntentFilter filter = new IntentFilter();filter.addAction(ACTION);Log.i("MyReceiver", "注册广播接收器！");registerReceiver(receiver, filter);registerBoolean = true;}});unregisterReceiver = (Button) findViewById(R.id.btnunregisterReceiver);unregisterReceiver.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {//第一次进入到应用程序后就点击“解绑广播接收器”按钮会崩溃，此行代码处理此异常。if (receiver == null) {Toast.makeText(MainActivity.this, "广播接收器为空！",Toast.LENGTH_SHORT).show();} //点击“解绑广播接收器“后再次点击”解绑广播接收器“后，程序崩溃，错误log信息为：FATAL EXCEPTION: main//08-04 05:04:35.420: E/AndroidRuntime(5521): java.lang.IllegalArgumentException: Receiver not registered: else if (registerBoolean == false) {Toast.makeText(MainActivity.this, "广播接收器未注册！",Toast.LENGTH_SHORT).show();}else{unregisterReceiver(receiver);registerBoolean = false;Log.i("MyReceiver", "广播接收器已经取消注册！");}}});}}

package com.jinhoward.broadcast.receiver;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.util.Log;/** * @author  jinhoward * @blog    http://blog.csdn.net/jinhoward */public class SecondReceiver extends BroadcastReceiver{private static final String TAG = "MyReceiver";public SecondReceiver(){Log.i(TAG, "广播接收器的构造函数");}@Overridepublic void onReceive(Context context, Intent intent){Log.i(TAG, "广播接收器接收到广播:"+intent.getAction());}}

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"      package="com.jinhoward.broadcast.activity"      android:versionCode="1"      android:versionName="1.0">    <uses-sdk android:minSdkVersion="8" />    <application android:icon="@drawable/icon" android:label="@string/app_name">        <activity android:name="com.jinhoward.broadcast.activity.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>    </application></manifest>

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