使用BroadCastReceiver

转载请注明出处: http://blog.youkuaiyun.com/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。