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;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		btnBroadcast = (Button) findViewById(R.id.btnBroadcast);
		btnBroadcast.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				Intent intent = new Intent();
				intent.setAction(ACTION);
				sendBroadcast(intent);
			}
		});

		registerReceiver = (Button) findViewById(R.id.btnregisterReceiver);
		registerReceiver.setOnClickListener(new OnClickListener() {
			@Override
			public 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() {
			@Override
			public 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");
	}

	@Override
	public 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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