截图原理（一）——Android自动化测试学习历程

package com.li.xiami.test;

import static org.junit.Assert.*;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.android.robotium.solo.Solo;
import com.li.xiami.MainActivity;

import android.test.ActivityInstrumentationTestCase2;

public class ScreenShot extends ActivityInstrumentationTestCase2<MainActivity> {

    //包名
    static String packageName = "com.li.xiami";
    //声明一个robotium的solo类
    private Solo solo;
    
    private static String tag = "xiami";
    
    //构造方法中写好包名和类名，让ActivityInstrumentationTestCase2能够找到被测试的app
    //的MainActivity
    @SuppressWarnings("deprecation")
    public ScreenShot(){
        //super(packageName, MainActivity.class);
        super(MainActivity.class);
    }
    
    @Before
    protected void setUp() throws Exception {
        super.setUp();
        //初始化solo对象
        solo = new Solo(getInstrumentation(), getActivity());
    }

    @After
    protected void tearDown() throws Exception {
        solo.finishOpenedActivities();
    }

    @Test
    public void test() {
        solo.clickOnButton("OK");
        solo.sleep(1000);
        solo.takeScreenshot("123picture");
        solo.sleep(3000);
    }

}

/**
     * Takes a screenshot and saves it with the specified name in "/sdcard/Robotium-Screenshots/". 
     * Requires write permission (android.permission.WRITE_EXTERNAL_STORAGE) in AndroidManifest.xml of the application under test.
     *
     * @param name the name to give the screenshot
     *
     */
//上面的话翻译下来就是：存储的位置确定了，就是在mnt/sdcard/Robotium-Screenshots/目录下
//但是需要写sd卡的权限，需要给under test的application在AndroidManifest.xml中配置permission，那么这里也就解释了我上面的运行过程中第二个问题

    public void takeScreenshot(String name){
        takeScreenshot(name, 100);
    }

/**
     * Takes a screenshot and saves the image with the specified name in "/sdcard/Robotium-Screenshots/". 
     * Requires write permission (android.permission.WRITE_EXTERNAL_STORAGE) in AndroidManifest.xml of the application under test.
     *
     * @param name the name to give the screenshot
     * @param quality the compression rate. From 0 (compress for lowest size) to 100 (compress for maximum quality)
     *
     */
//上面的话翻译下来就是：图片存储位置以及读写权限与第一步中相同
//参数分别表示picture的name，以及清晰度（从0到100），默认是100，当然你也可以直接在函数中调用这个函数，然后设置这个quality的值

    public void takeScreenshot(String name, int quality){
        screenshotTaker.takeScreenshot(name, quality);
    }

/**
     * Takes a screenshot and saves it in "/sdcard/Robotium-Screenshots/". 
     * Requires write permission (android.permission.WRITE_EXTERNAL_STORAGE) in AndroidManifest.xml of the application under test.
     * 
     * @param view the view to take screenshot of
     * @param name the name to give the screenshot image
     * @param quality the compression rate. From 0 (compress for lowest size) to 100 (compress for maximum quality).
     */
//第三步走到了一个新的类中，是screenShotTaker的类
//这个才是真正的执行Screenshot的函数，这个才是截图的逻辑

    public void takeScreenshot(final String name, final int quality) {
        //1、得到目前屏幕所有视图
        View decorView = getScreenshotView();
        if(decorView == null) 
            return;
        //2、初始化
        initScreenShotSaver();
        //3、实例化截图对象
        ScreenshotRunnable runnable = new ScreenshotRunnable(decorView, name, quality);
        //4、调用截图对象的run方法
        activityUtils.getCurrentActivity(false).runOnUiThread(runnable);
    }

/**
     * Gets the proper view to use for a screenshot.  
     */
    private View getScreenshotView() {
        //获取到屏幕上的view
        View decorView = viewFetcher.getRecentDecorView(viewFetcher.getWindowDecorViews());
        final long endTime = SystemClock.uptimeMillis() + Timeout.getSmallTimeout();

        while (decorView == null) {    

            final boolean timedOut = SystemClock.uptimeMillis() > endTime;

            if (timedOut){
                return null;
            }
            sleeper.sleepMini();
            decorView = viewFetcher.getRecentDecorView(viewFetcher.getWindowDecorViews());
        }
        wrapAllGLViews(decorView);

        return decorView;
    }

/**
     * Returns the WindorDecorViews shown on the screen.
     * 
     * @return the WindorDecorViews shown on the screen
     */
    //翻译下来就是：获取到展示在screen上的所有WindowDecorViews，是一个View的数组，然后这个view的数组返回后，再作为viewFetcher.getRecentDecorView的参数
    //用反射方法去获取 View 视图数组
　　　　
    @SuppressWarnings("unchecked")
    public View[] getWindowDecorViews()
    {
        Field viewsField;
        Field instanceField;
        try {
            viewsField = windowManager.getDeclaredField("mViews");
            instanceField = windowManager.getDeclaredField(windowManagerString);
            viewsField.setAccessible(true);
            instanceField.setAccessible(true);
            Object instance = instanceField.get(null);
            View[] result;
            if (android.os.Build.VERSION.SDK_INT >= 19) {
                result = ((ArrayList<View>) viewsField.get(instance)).toArray(new View[0]);
            } else {
                result = (View[]) viewsField.get(instance);
            }
            return result;
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return null;
    }
    

/**
     * Returns the most recent DecorView
     *
     * @param views the views to check
     * @return the most recent DecorView
     */
     //翻译下来就是：返回最近的DecorView


     public final View getRecentDecorView(View[] views) {
         if(views == null)
             return null;
         
         final View[] decorViews = new View[views.length];
         int i = 0;
         View view;
　　　　　　//通过遍历View数组，来得到most recent DecorView
         for (int j = 0; j < views.length; j++) {
             view = views[j];
             if (view != null && view.getClass().getName()
                     .equals("com.android.internal.policy.impl.PhoneWindow$DecorView")) {
                 decorViews[i] = view;
                 i++;
             }
         }
         return getRecentContainer(decorViews);
     }

/**
     * This method initializes the aysnc screenshot saving logic
     */
　　//翻译下来就是：初始化一个aysnc（异步）的sreenshot的保存逻辑

    private void initScreenShotSaver() {
        if(screenShotSaverThread == null || screenShotSaver == null) {
            //声明一个HandlerThread对象
            screenShotSaverThread = new HandlerThread("ScreenShotSaver");
            screenShotSaverThread.start();
            //把screenShotSaverThread捆绑到handler
            screenShotSaver = new ScreenShotSaver(screenShotSaverThread);
        }
    }

/**
     * This class is a Handler which deals with saving the screenshots on a separate thread.
     *
     * The screenshot logic by necessity has to run on the ui thread.  However, in practice
     * it seems that saving a screenshot (with quality 100) takes approx twice as long
     * as taking it in the first place. 
     *
     * Saving the screenshots in a separate thread like this will thus make the screenshot
     * process approx 3x faster as far as the main thread is concerned.
     *
     */
　　　//翻译下来就是：这是一个继承自Handler，在一个单独的thread上处理如何存储sreenchots的类
     //screenshot的逻辑必须要跑在ui线程上，然而，事实上，好像这个保存screenshot反而花费了将近2倍的时间
     //保存这个screenshots在另一个线程中，就会使得这个处理能够快三倍，当然是与跑在主线程上相比而言

    private class ScreenShotSaver extends Handler {
        public ScreenShotSaver(HandlerThread thread) {
            super(thread.getLooper());
        }

/**
     * Here we have a Runnable which is responsible for taking the actual screenshot,
     * and then posting the bitmap to a Handler which will save it.
     * 这是把runnable对象放进Handler对象里面通过得到的view去变成bitmap
     * 把runnable的run方法实现，首先把view转成bitmap对象，之后调用之前的screenShotSaver的
     * Handler对象save这个bitmap的对象
     * This Runnable is run on the UI thread.
     */
    private class ScreenshotRunnable implements Runnable {

        private View view;
        private String name;
        private int quality;

        public ScreenshotRunnable(final View _view, final String _name, final int _quality) {
            view = _view;
            name = _name;
            quality = _quality;
        }

        public void run() {
            if(view !=null){
                Bitmap  b;
                //根据是否是WebView做出不同的处理
                if(view instanceof WebView){
                    b = getBitmapOfWebView((WebView) view);
                }
                else{
                    b = getBitmapOfView(view);
                }
                if(b != null)
                    //如果bitmap对象不为空，就存到sd卡里
                    screenShotSaver.saveBitmap(b, name, quality);
                else 
                    Log.d(LOG_TAG, "NULL BITMAP!!");
            }
        }
    }

/**
         * This method posts a Bitmap with meta-data to the Handler queue.
         *
         * @param bitmap the bitmap to save
         * @param name the name of the file
         * @param quality the compression rate. From 0 (compress for lowest size) to 100 (compress for maximum quality).
         */
        public void saveBitmap(Bitmap bitmap, String name, int quality) {
            //获取一个message对象，然后把bitmap的信息存储到这个message中
            //将这个message发出去，发送到looper，然后这个message会被handleMessage接收
　　　　　　　//这里没有直接存储，而使用message，是想要用到looper，使用looper的好处是：可以短时间内放10个左右的截图

            Message message = this.obtainMessage();
            message.arg1 = quality;
            message.obj = bitmap;
            message.getData().putString("name", name);
            this.sendMessage(message);
        }

/**
         * Here we process the Handler queue and save the bitmaps.
         *
         * @param message A Message containing the bitmap to save, and some metadata.
         */
        public void handleMessage(Message message) {
            //复写Handler的handleMessage方法，然后获取到message对象，之后调用saveFile方法方法保存bitmap对象
            String name = message.getData().getString("name");
            int quality = message.arg1;
            Bitmap b = (Bitmap)message.obj;
            if(b != null) {
                saveFile(name, b, quality);
                b.recycle();
            }
            else {
                Log.d(LOG_TAG, "NULL BITMAP!!");
            }
        }

/**
         * Saves a file.
         * 
         * @param name the name of the file
         * @param b the bitmap to save
         * @param quality the compression rate. From 0 (compress for lowest size) to 100 (compress for maximum quality).
         * 
         */
        private void saveFile(String name, Bitmap b, int quality){
            //构造一个File输出流，写bitmap对象到sd卡
            FileOutputStream fos = null;
            String fileName = getFileName(name);
　　　　　　　//
            File directory = new File(Environment.getExternalStorageDirectory() + "/Robotium-Screenshots/");
            directory.mkdir();

            File fileToSave = new File(directory,fileName);
            try {
                //初始化一个File的输入输出类，用以进行file的存储，之后调用compress方法写入
                fos = new FileOutputStream(fileToSave);
                if (b.compress(Bitmap.CompressFormat.JPEG, quality, fos) == false)
                    Log.d(LOG_TAG, "Compress/Write failed");
                fos.flush();
                fos.close();
            } catch (Exception e) {
                Log.d(LOG_TAG, "Can‘t save the screenshot! Requires write permission (android.permission.WRITE_EXTERNAL_STORAGE) in AndroidManifest.xml of the application under test.");
                e.printStackTrace();
            }
        }