Android使用技巧------Activity中怎么样在子线程和UI线程中来回自如

一个方法:runOnUiThread

runOnUiThread是Activity内部的一个方法,源码如下:

    /**     * Runs the specified action on the UI thread. If the current thread is the UI     * thread, then the action is executed immediately. If the current thread is     * not the UI thread, the action is posted to the event queue of the UI thread.     *     * @param action the action to run on the UI thread     */    public final void runOnUiThread(Runnable action) {        if (Thread.currentThread() != mUiThread) {            mHandler.post(action);        } else {            action.run();        }    }

接收参数是一个Runnable,接着判断当前是不是UI线程，如果不是的话就把这一步任务post到UI县城中去执行，如果是UI线程的话就执行这个异步任务。

下面是在自己的工程中截取的一个方法：（在一个New的线程run（）中用runOnUiThread（）更新UI。so easy ！）

 private void getMute() {        new Thread() {            @Override            public void run() {                final String mute = mController.getMute(mDevice);                runOnUiThread(new Runnable() {                    @Override                    public void run() {                        if (mute == null) {                            LogUtil.d(TAG, "get mute failed...");                            //跟新SeekBar的状态                            if (sb_voice.getProgress() == 0) {                                initMuteImg(MUTE);                            }                        } else {                            LogUtil.d(TAG, "get mute success");                            initMuteImg(mute);                        }                    }                });            }        }.start();    }

一个类:HandlerThread

上源码：（源码不是很多）

/* * Copyright (C) 2006 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package android.os;/** * Handy class for starting a new thread that has a looper. The looper can then be  * used to create handler classes. Note that start() must still be called. */public class HandlerThread extends Thread {    int mPriority;    int mTid = -1;    Looper mLooper;    public HandlerThread(String name) {        super(name);        mPriority = Process.THREAD_PRIORITY_DEFAULT;    }    /**     * Constructs a HandlerThread.     * @param name     * @param priority The priority to run the thread at. The value supplied must be from      * {@link android.os.Process} and not from java.lang.Thread.     */    public HandlerThread(String name, int priority) {        super(name);        mPriority = priority;    }    /**     * Call back method that can be explicitly overridden if needed to execute some     * setup before Looper loops.     */    protected void onLooperPrepared() {    }    @Override    public void run() {        mTid = Process.myTid();        Looper.prepare();        synchronized (this) {            mLooper = Looper.myLooper();            notifyAll();        }        Process.setThreadPriority(mPriority);        onLooperPrepared();        Looper.loop();        mTid = -1;    }    /**     * This method returns the Looper associated with this thread. If this thread not been started     * or for any reason is isAlive() returns false, this method will return null. If this thread      * has been started, this method will block until the looper has been initialized.       * @return The looper.     */    public Looper getLooper() {        if (!isAlive()) {            return null;        }        // If the thread has been started, wait until the looper has been created.        synchronized (this) {            while (isAlive() && mLooper == null) {                try {                    wait();                } catch (InterruptedException e) {                }            }        }        return mLooper;    }    /**     * Quits the handler thread's looper.     * <p>     * Causes the handler thread's looper to terminate without processing any     * more messages in the message queue.     * </p><p>     * Any attempt to post messages to the queue after the looper is asked to quit will fail.     * For example, the {@link Handler#sendMessage(Message)} method will return false.     * </p><p class="note">     * Using this method may be unsafe because some messages may not be delivered     * before the looper terminates.  Consider using {@link #quitSafely} instead to ensure     * that all pending work is completed in an orderly manner.     * </p>     *     * @return True if the looper looper has been asked to quit or false if the     * thread had not yet started running.     *     * @see #quitSafely     */    public boolean quit() {        Looper looper = getLooper();        if (looper != null) {            looper.quit();            return true;        }        return false;    }    /**     * Quits the handler thread's looper safely.     * <p>     * Causes the handler thread's looper to terminate as soon as all remaining messages     * in the message queue that are already due to be delivered have been handled.     * Pending delayed messages with due times in the future will not be delivered.     * </p><p>     * Any attempt to post messages to the queue after the looper is asked to quit will fail.     * For example, the {@link Handler#sendMessage(Message)} method will return false.     * </p><p>     * If the thread has not been started or has finished (that is if     * {@link #getLooper} returns null), then false is returned.     * Otherwise the looper is asked to quit and true is returned.     * </p>     *     * @return True if the looper looper has been asked to quit or false if the     * thread had not yet started running.     */    public boolean quitSafely() {        Looper looper = getLooper();        if (looper != null) {            looper.quitSafely();            return true;        }        return false;    }    /**     * Returns the identifier of this thread. See Process.myTid().     */    public int getThreadId() {        return mTid;    }}

首先，HandlerThread是一个Thread，意味这在它的run（）里面跑得任务都是异步。再看其run（），能到通过 Looper.myLooper()获得一个mLooper，还提供了一个getLooper()方法获取这个Looper。熟悉Handler、Looper、Message机制的话，很容一就可以把你想要放在HandlerThread中去，举个栗子：

首先创建自己的HandlerThread，让它跑起来：

 HandlerThread playThread = new HandlerThread("PlayActionManager"); playThread.start();

接下来就是将其内部的Looper给到目标Handler：

 PlayControHandler  controHandler = new PlayControHandler(playThread.getLooper());

好了，你可以尽情地在PlayContorHandler（继承自Handler）中的handleMessage方法中做耗时的事情了。