使用BroadCastReceiver
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转载请注明出处: http://blog.csdn.net/a992036795/article/details/51596610
概念:BroadCast是一种广泛运用的,在应用程序之间传输信息的机制,Android中的广播与传统意义上的电台广播类似,一个广播可以有任意个接收者。广播机制是一个典型的发布-订阅模式。
Android的广播可分为普通广播、有序广播、本地广播和 Sticky广播。
一、普通广播
普通广播是完全异步的,通过Context的SendBroadCast()函数来发送,消息传递的效率比较高,但所有的receivers(接收器)的执行顺序不确定,缺点是:接受着不能将处理消息传递给一下个接受着,并且无法终止广播Intent的传播。
普通广播的使用:首先定义一个广播类,用来接收广播:
public class SimpleBroadCast extends BroadcastReceiver { private static final String TAG = "SimpleBroadCast"; @Override public void onReceive(Context context, Intent intent) { Log.i(TAG, "onReceive: "); }}
然后在注册该广播接收器:
@Override protected void onStart() { super.onStart(); /*注册广播*/ registerReceiver(broadCast,new IntentFilter(ACTION)); } @Override protected void onStop() { super.onStop(); /*取消注册*/ unregisterReceiver(broadCast); }
这里我选择动态注册,当然也可以静态注册即在清单文件中注册。
最后:贴出发送广播的代码:
/*发送一个普通广播*/ sendBroadcast(new Intent(ACTION));
二、有序广播。
有序广播通过Context.sendOrderBroadcast()来发送,所有的广播接收器按照优先级一次执行,广播接收器的有限制级可以通过receiver的intent-filter中的android:priotiry属性来设置,数值越大优先级越高,当广播接收器接收到广播之后,可以使用setResult()函数来将结果传递给下一个广播接收器,然后下一个广播接收器通过getResult函数获得上一个广播接收器返回的结果,并使用abortBroadcast函数来让系统丢弃该广播,使得该广播不在传递。
使用:
一、在清单文件中注册:
<receiver android:name=".SimpleBroadCast"> <intent-filter android:priority="100"> <action>"hello"</action> </intent-filter> </receiver>
发送广播代码:
sendOrderedBroadcast(new Intent(ACTION),null);
上文提到的BroadCastReveiver中的setResut 和getResult,这里给出方法在BroadCastReceiver中的定义
public final void setResultCode(int code) { checkSynchronousHint(); mPendingResult.mResultCode = code; } /** * Retrieve the current result code, as set by the previous receiver. * * @return int The current result code. */ public final int getResultCode() { return mPendingResult != null ? mPendingResult.mResultCode : 0; } /** * Change the current result data of this broadcast; only works with * broadcasts sent through * {@link Context#sendOrderedBroadcast(Intent, String) * Context.sendOrderedBroadcast}. This is an arbitrary * string whose interpretation is up to the broadcaster. * * <p><strong>This method does not work with non-ordered broadcasts such * as those sent with {@link Context#sendBroadcast(Intent) * Context.sendBroadcast}</strong></p> * * @param data The new result data; may be null. * * @see #setResult(int, String, Bundle) */ public final void setResultData(String data) { checkSynchronousHint(); mPendingResult.mResultData = data; } /** * Retrieve the current result data, as set by the previous receiver. * Often this is null. * * @return String The current result data; may be null. */ public final String getResultData() { return mPendingResult != null ? mPendingResult.mResultData : null; } /** * Change the current result extras of this broadcast; only works with * broadcasts sent through * {@link Context#sendOrderedBroadcast(Intent, String) * Context.sendOrderedBroadcast}. This is a Bundle * holding arbitrary data, whose interpretation is up to the * broadcaster. Can be set to null. Calling this method completely * replaces the current map (if any). * * <p><strong>This method does not work with non-ordered broadcasts such * as those sent with {@link Context#sendBroadcast(Intent) * Context.sendBroadcast}</strong></p> * * @param extras The new extra data map; may be null. * * @see #setResult(int, String, Bundle) */ public final void setResultExtras(Bundle extras) { checkSynchronousHint(); mPendingResult.mResultExtras = extras; } /** * Retrieve the current result extra data, as set by the previous receiver. * Any changes you make to the returned Map will be propagated to the next * receiver. * * @param makeMap If true then a new empty Map will be made for you if the * current Map is null; if false you should be prepared to * receive a null Map. * * @return Map The current extras map. */ public final Bundle getResultExtras(boolean makeMap) { if (mPendingResult == null) { return null; } Bundle e = mPendingResult.mResultExtras; if (!makeMap) return e; if (e == null) mPendingResult.mResultExtras = e = new Bundle(); return e; }
三、本地广播。
在21版的Support v4包中新增的本地广播,也就是LocalBroadCastManager。之前广播都是全局的,所有应用程序都可以接受到,这样就会带来安全隐患。LocalBroadCastManager使得广播只在进程内传播。用法其实很多简单。
主要使用4个方法
注册Receiver:
LocalBroadCastManager.getInstance(context).registerReceiver(receiver,intentFilter);
注销Receiver:
LocalBroadcastManager.getInstance(context).unregisterReceiver(receiver)
发送异步广播:
LocalBroadcastManager.getInstance(context).sendBroadcast(new Intent(HELLO_ACTION);
发送同步广播:
LocalBroadcastManager.getInstance(context).sendBroadcastSync(new Intent());
本地广播与普通广播只是操作类不一样,其他接口基本都类似,因此,替换为本地广播的成本相对较低。为了程序安全,建议在不需要其他进程接受广播的情况下使用本地广播。
四、Sticky广播
sticky广播通过Context.sendStickBroadcast()函数来发送,用此函数发送的广播一直滞留,当有匹配此广播的广播接收器被注册后,该广播接收器会收到此条广播。使用此函数发送广播时,需要获得BROADCAST_STICKY权限
<uses-permission android:name="android.permission.BROADCAST_STICKY"></uses-permission>
sendStickBroadcast只保留最后一条广播,并且一直保留下去,这样即使已经有广播接收器处理该广播,当再有匹配的广播被注册,此广播仍会被接收。如果你只想处理一遍该广播,可以通过removeStickBroadcast()函数实现。
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