Android编程--常用代码

1. 如何使用Handler？

创建Handler的方式：

1) new Handler() 
    创建目前正在执行此指令的线程的Handler对象，其Looper通过Looper.Looper.myLooper()获取
2) new Handler(Looper)
    创建指定Looper线程的Handler对象， 如new Handler(Looper.getMainLooper())创建主线程的Handler对象

发送Message方案一：

    static final int KEEP_SCREEN_ON_MSG = 1;    static final int GET_NEW_SURFACE_MSG = 2;    static final int UPDATE_WINDOW_MSG = 3;    final Handler mHandler = new Handler() {        @Override        public void handleMessage(Message msg) {            switch (msg.what) {                case KEEP_SCREEN_ON_MSG: {                    setKeepScreenOn(msg.arg1 != 0);                } break;                case GET_NEW_SURFACE_MSG: {                    handleGetNewSurface();                } break;                case UPDATE_WINDOW_MSG: {                    updateWindow(false, false);                } break;            }        }    };    //发送空消息    mHandler.sendEmptyMessage(UPDATE_WINDOW_MSG);    //发送一个Message    Message msg = mHandler.obtainMessage(GET_NEW_SURFACE_MSG);    mHandler.sendMessage(msg);

发送Message方案二：

    class AudioHandler extends Handler {                private void setDeviceVolume(VolumeStreamState streamState, int device) {                //do something            }                private void setAllVolumes(VolumeStreamState streamState) {                //do something            }                @Override            public void handleMessage(Message msg) {                    switch (msg.what) {                        case MSG_SET_DEVICE_VOLUME:                        setDeviceVolume((VolumeStreamState) msg.obj, msg.arg1);                        break;                        case MSG_SET_ALL_VOLUMES:                        setAllVolumes((VolumeStreamState) msg.obj);                        break;                    // ...                }            }        }

发送Runnable方案三：

public class MainActivity extends Activity {    private Handler h;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);        h = new Handler(){            public void handleMessage(Message msg) {                //do nothing            }        };                 h.post(new myRun());}        class myRun implements Runnable{        public void run(){             setTitle(String.valueOf(1));            h.postDelayed(testRun, 2000);        }    }    Runnable testRun= new Runnable() {        public void run(){            setTitle(String.valueOf(2));        }    };}

2. 如何使用Looper

Looper.prepare();// 创建Handler        Looper.loop();// 在此线程中创建的Handler将向Looper的MessageQueue发送消息

3. 创建、实现、启动线程

方案一：

    new Thread(){        public void run(){             //do something you want to do        }    }.start();

方案二：

    class Task implements Runnable {        public void run() {             // do something you want to do        }    }        Task ta = new Task();    Thread t1 = new Thread(ta, "MyTask");    t1.start();

方案三：

    class MyThread extends Thread {        public MyThread() {            super("MyThread");        }        @Override        public void run() {            Looper.prepare();            mMyLooper = Looper.myLooper();            mAudioHandler = new AudioHandler();            //do something you want to do              Looper.loop();        }    }    AudioHandler mAudioHandler;    Looper mMyLooper;    MyThread mMyThread = new MyThread();    mMyThread.start(); //启动线程    // wait some event    mMyLooper.quit(); //使线程退出

4. 实现SurfaceHolder

    在SurfaceView中实现的SurfaceHolder如下：

    private SurfaceHolder mSurfaceHolder = new SurfaceHolder() {                private static final String LOG_TAG = "SurfaceHolder";                public boolean isCreating() {            return mIsCreating;        }        public void addCallback(Callback callback) {            synchronized (mCallbacks) {                // This is a linear search, but in practice we'll                 // have only a couple callbacks, so it doesn't matter.                if (mCallbacks.contains(callback) == false) {                          mCallbacks.add(callback);                }            }        }        public void removeCallback(Callback callback) {            synchronized (mCallbacks) {                mCallbacks.remove(callback);            }        }                public void setFixedSize(int width, int height) {            if (mRequestedWidth != width || mRequestedHeight != height) {                mRequestedWidth = width;                mRequestedHeight = height;                requestLayout();            }        }        public void setSizeFromLayout() {            if (mRequestedWidth != -1 || mRequestedHeight != -1) {                mRequestedWidth = mRequestedHeight = -1;                requestLayout();            }        }        public void setFormat(int format) {            // for backward compatibility reason, OPAQUE always            // means 565 for SurfaceView            if (format == PixelFormat.OPAQUE)                format = PixelFormat.RGB_565;            mRequestedFormat = format;            if (mWindow != null) {                updateWindow(false, false);            }        }        /**         * @deprecated setType is now ignored.         */        @Deprecated        public void setType(int type) { }        public void setKeepScreenOn(boolean screenOn) {            Message msg = mHandler.obtainMessage(KEEP_SCREEN_ON_MSG);            msg.arg1 = screenOn ? 1 : 0;            mHandler.sendMessage(msg);        }                public Canvas lockCanvas() {            return internalLockCanvas(null);        }        public Canvas lockCanvas(Rect dirty) {            return internalLockCanvas(dirty);        }        private final Canvas internalLockCanvas(Rect dirty) {            mSurfaceLock.lock();            if (DEBUG) Log.i(TAG, "Locking canvas... stopped="                    + mDrawingStopped + ", win=" + mWindow);            Canvas c = null;            if (!mDrawingStopped && mWindow != null) {                if (dirty == null) {                    if (mTmpDirty == null) {                        mTmpDirty = new Rect();                    }                    mTmpDirty.set(mSurfaceFrame);                    dirty = mTmpDirty;                }                try {                    c = mSurface.lockCanvas(dirty);                } catch (Exception e) {                    Log.e(LOG_TAG, "Exception locking surface", e);                }            }            if (DEBUG) Log.i(TAG, "Returned canvas: " + c);            if (c != null) {                mLastLockTime = SystemClock.uptimeMillis();                return c;            }                        // If the Surface is not ready to be drawn, then return null,            // but throttle calls to this function so it isn't called more            // than every 100ms.            long now = SystemClock.uptimeMillis();            long nextTime = mLastLockTime + 100;            if (nextTime > now) {                try {                    Thread.sleep(nextTime-now);                } catch (InterruptedException e) {                }                now = SystemClock.uptimeMillis();            }            mLastLockTime = now;            mSurfaceLock.unlock();                        return null;        }        public void unlockCanvasAndPost(Canvas canvas) {            mSurface.unlockCanvasAndPost(canvas);            mSurfaceLock.unlock();        }        public Surface getSurface() {            return mSurface;        }        public Rect getSurfaceFrame() {            return mSurfaceFrame;        }    }

5. 使用ProgressDialog

public class MainActivity extends Activity {ProgressDialog mDialog;MyThread mThread;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);// create and display the progress in a new thread        mDialog = new ProgressDialog(MainActivity.this);          mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);          mDialog.setTitle("MyTitle");          //mDialog.setIcon(R.drawable.icon);          mDialog.setMessage("This is a progress example!");          mDialog.setMax(100);          mDialog.setProgress(0);          //mDialog.setSecondaryProgress(50);          mDialog.setIndeterminate(false);          mDialog.setCancelable(true);          mDialog.show();         mThread = new MyThread();mThread.start();}public class MyThread extends Thread {MyThread(){super("MyThread");}@Overridepublic void run(){int i=0;while(i<100){i++;// set the progress valuemDialog.setProgress(i);try{Thread.sleep(100); // sleep 1s}catch(InterruptedException e){e.printStackTrace();}}// destroy the progressmDialog.dismiss();}}}

6. 如何使用Timer and TimerTask?

package com.example.mytest;import java.util.Timer;import java.util.TimerTask;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.app.Activity;import android.view.Menu;public class MainActivity extends Activity {    private Timer timer = new Timer();    private Handler h;    private int k = 0;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);        h = new Handler(){            public void handleMessage(Message msg) {                setTitle((String)msg.obj);            }        };         // init and start the timer        init();}    public void init() {    //public abstract class TimerTask implements Runnable        TimerTask task = new TimerTask(){            @Override             public void run() {                h.removeMessages(0);                Message m = h.obtainMessage(1, 1, 1,Thread.currentThread().getName() + " : "+String.valueOf(k++));                h.sendMessage(m);            }        };        // after 500ms execute task firstly, then every 1000ms execute the task        timer.schedule(task, 500, 1000); //启动Timer线程    }}