Android中使用代码截图的各种方法总结

发布时间:2016-12-7 20:31:15 编辑:www.fx114.net 分享查询网我要评论
本篇文章主要介绍了"Android中使用代码截图的各种方法总结",主要涉及到Android中使用代码截图的各种方法总结方面的内容,对于Android中使用代码截图的各种方法总结感兴趣的同学可以参考一下。

1,基于Android SDK的截屏方法 (1)主要就是利用SDK提供的View.getDrawingCache()方法。网上已经有很多的实例了。首先创建一个android project,然后进行Layout,画一个按键(res/layout/main.xml): <?xmlversion="1.0"encoding="utf-8"?> <LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     > <TextView     android:layout_width="fill_parent"     android:layout_height="wrap_content"     android:text="@string/hello"     /> <Button   android:text="NiceButton"   android:id="@+id/my_button"   android:layout_width="fill_parent"   android:layout_height="wrap_content"   android:layout_alignParentBottom="true"></Button> </LinearLayout> HelloAndroid.java实现代码为: packagecom.example.helloandroid;   importjava.io.FileOutputStream; importjava.text.SimpleDateFormat; importjava.util.Date; importjava.util.Locale;   importandroid.app.Activity; importandroid.graphics.Bitmap; importandroid.os.Bundle; importandroid.view.View; importandroid.view.View.OnClickListener; importandroid.widget.Button;   publicclassHelloAndroidextendsActivity {     privateButton button;     /** Called when the activity is first created. */   @Override   publicvoidonCreate(Bundle savedInstanceState) {       super.onCreate(savedInstanceState);     this.setContentView(R.layout.main);     this.button = (Button) this.findViewById(R.id.my_button);     this.button.setOnClickListener(newOnClickListener() {         publicvoidonClick(View v) {         SimpleDateFormat sdf = newSimpleDateFormat(             "yyyy-MM-dd_HH-mm-ss", Locale.US);         String fname = "/sdcard/"+ sdf.format(newDate()) + ".png";         View view = v.getRootView();         view.setDrawingCacheEnabled(true);         view.buildDrawingCache();         Bitmap bitmap = view.getDrawingCache();         if(bitmap != null) {           System.out.println("bitmap got!");           try{             FileOutputStream out = newFileOutputStream(fname);             bitmap.compress(Bitmap.CompressFormat.PNG,100, out);             System.out.println("file " + fname + "output done.");           }catch(Exception e) {             e.printStackTrace();           }         }else{           System.out.println("bitmap is NULL!");         }       }       });     } } 这个代码会在按下app中按键的时候自动在手机的/sdcard/目录下生成一个时间戳命名的png截屏文件。 这种截屏有一个问题,就是只能截到一部分,比如电池指示部分就截不出来了。 (2)在APK中调用“adb shell screencap -pfilepath” 命令 该命令读取系统的framebuffer,需要获得系统权限: (1). 在AndroidManifest.xml文件中添加 <uses-permissionandroid:name="android.permission.READ_FRAME_BUFFER"/> (2). 修改APK为系统权限,将APK放到源码中编译, 修改Android.mk  LOCAL_CERTIFICATE := platform publicvoid takeScreenShot(){    String mSavedPath = Environment.getExternalStorageDirectory()+File. separator + "screenshot.png" ; try {                               Runtime. getRuntime().exec("screencap -p " + mSavedPath);    } catch (Exception e) {           e.printStackTrace();    } (3).利用系统的API,实现Screenshot,这部分代码是系统隐藏的,需要在源码下编译,     1).修改Android.mk, 添加系统权限           LOCAL_CERTIFICATE := platform          2).修改AndroidManifest.xml 文件,添加 权限 <uses-permissionandroid:name="android.permission.READ_FRAME_BUFFER"/> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37       public boolean takeScreenShot(String imagePath){                                                                               if(imagePath.equals("" )){                       imagePath = Environment.getExternalStorageDirectory()+File. separator+"Screenshot.png" ;              }                                 Bitmap mScreenBitmap;           WindowManager mWindowManager;           DisplayMetrics mDisplayMetrics;           Display mDisplay;                              mWindowManager = (WindowManager) mcontext.getSystemService(Context.WINDOW_SERVICE);           mDisplay = mWindowManager.getDefaultDisplay();           mDisplayMetrics = new DisplayMetrics();           mDisplay.getRealMetrics(mDisplayMetrics);                                             float[] dims = {mDisplayMetrics.widthPixels , mDisplayMetrics.heightPixels };           mScreenBitmap = Surface. screenshot((int) dims[0], ( int) dims[1]);                                 if (mScreenBitmap == null) {                    return false ;           }                           try {           FileOutputStream out = new FileOutputStream(imagePath);           mScreenBitmap.compress(Bitmap.CompressFormat. PNG, 100, out);                       } catch (Exception e) {                                             return false ;         }                                            return true ; } 2 基于Android ddmlib进行截屏 public class ScreenShot { private BufferedImage image = null; /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub AndroidDebugBridge.init(false); // ScreenShot screenshot = new ScreenShot(); IDevice device = screenshot.getDevice(); for (int i = 0; i < 10; i++) { Date date=new Date(); SimpleDateFormat df=new SimpleDateFormat("MM-dd-HH-mm-ss"); String nowTime = df.format(date); screenshot.getScreenShot(device, "Robotium" + nowTime); try { Thread.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } public void getScreenShot(IDevice device,String filename) { RawImage rawScreen = null; try { rawScreen = device.getScreenshot(); } catch (TimeoutException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (AdbCommandRejectedException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } if (rawScreen != null) { Boolean landscape = false; int width2 = landscape ? rawScreen.height : rawScreen.width; int height2 = landscape ? rawScreen.width : rawScreen.height; if (image == null) { image = new BufferedImage(width2, height2, BufferedImage.TYPE_INT_RGB); } else { if (image.getHeight() != height2 || image.getWidth() != width2) { image = new BufferedImage(width2, height2, BufferedImage.TYPE_INT_RGB); } } int index = 0; int indexInc = rawScreen.bpp >> 3; for (int y = 0; y < rawScreen.height; y++) { for (int x = 0; x < rawScreen.width; x++, index += indexInc) { int value = rawScreen.getARGB(index); if (landscape) image.setRGB(y, rawScreen.width - x - 1, value); else image.setRGB(x, y, value); } } try { ImageIO.write((RenderedImage) image, "PNG", new File("D:/" + filename + ".jpg")); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } /** * 获取得到device对象 * @return */ private IDevice getDevice(){ IDevice device; AndroidDebugBridge bridge = AndroidDebugBridge .createBridge("adb", true);//如果代码有问题请查看API,修改此处的参数值试一下 waitDevicesList(bridge); IDevice devices[] = bridge.getDevices(); device = devices[0]; return device; } /** * 等待查找device * @param bridge */ private void waitDevicesList(AndroidDebugBridge bridge) { int count = 0; while (bridge.hasInitialDeviceList() == false) { try { Thread.sleep(500); count++; } catch (InterruptedException e) { } if (count > 240) { System.err.print("等待获取设备超时"); break; } } } 3 Android本地编程(Native Programming)读取framebuffer (1)命令行,框架的截屏功能是通过framebuffer来实现的,所以我们先来介绍一下framebuffer。 framebuffer介绍 帧缓冲(framebuffer)是Linux为显示设备提供的一个接口,把显存抽象后的一种设备,他允许上层应用程序在图形模式下直接对显示缓冲区进行 读写操作。这种操作是抽象的,统一的。用户不必关心物理显存的位置、换页机制等等具体细节。这些都是由Framebuffer设备驱动来完成的。 Linux FrameBuffer 本质上只是提供了对图形设备的硬件抽象,在开发者看来,FrameBuffer 是一块显示缓存,往显示缓存中写入特定格式的数据就意味着向屏幕输出内容。所以说FrameBuffer就是一块白板。例如对于初始化为16 位色的FrameBuffer 来说, FrameBuffer中的两个字节代表屏幕上一个点,从上到下,从左至右,屏幕位置与内存地址是顺序的线性关系。 帧缓存有个地址,是在内存里。我们通过不停的向frame buffer中写入数据, 显示控制器就自动的从frame buffer中取数据并显示出来。全部的图形都共享内存中同一个帧缓存。 Android截屏实现思路 Android系统是基于Linux内核的,所以也存在framebuffer这个设备,我们要实现截屏的话只要能获取到framebuffer中的数据,然后把数据转换成图片就可以了,android中的framebuffer数据是存放在 /dev/graphics/fb0 文件中的,所以我们只需要来获取这个文件的数据就可以得到当前屏幕的内容。 现在我们的测试代码运行时候是通过RC(remote controller)方式来运行被测应用的,那就需要在PC机上来访问模拟器或者真机上的framebuffer数据,这个的话可以通过android的ADB命令来实现。 具体实现 /***********************************************************************   *   *   ScreenShot.java   ***********************************************************************/ import java.awt.image.BufferedImage; import java.io.ByteArrayOutputStream; import java.io.DataInput; import java.io.EOFException; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import javax.imageio.ImageIO; import org.openqa.selenium.OutputType; import org.openqa.selenium.internal.Base64Encoder; import com.google.common.io.Closeables; import com.google.common.io.LittleEndianDataInputStream; /**  */ public class ScreenShot {     /**      * @param args      * @throws InterruptedException       */     public static void main(String[] args) throws InterruptedException {             try {             //分辨率大小,后续可以通过代码来获取到当前的分辨率             int xResolution = 320;             int yResolution = 480;             //执行adb命令,把framebuffer中内容保存到fb1文件中              Runtime.getRuntime().exec("adb pull /dev/graphics/fb0 C:/fb1");              //等待几秒保证framebuffer中的数据都被保存下来,如果没有保存完成进行读取操作会有IO异常              Thread.sleep(15000);              //读取文件中的数据              InputStream in = (InputStream)new FileInputStream("C:/fb1");              DataInput frameBuffer = new LittleEndianDataInputStream(in);                            BufferedImage screenImage = new BufferedImage(                      xResolution, yResolution, BufferedImage.TYPE_INT_ARGB);                  int[] oneLine = new int[xResolution];                 for (int y = 0; y < yResolution; y++) {                     //从frameBuffer中计算出rgb值                     convertToRgba32(frameBuffer, oneLine);                     //把rgb值设置到image对象中                     screenImage.setRGB(0, y, xResolution, 1, oneLine, 0, xResolution);                 }                 Closeables.closeQuietly(in);                                  ByteArrayOutputStream rawPngStream = new ByteArrayOutputStream();                 try {                       if (!ImageIO.write(screenImage, "png", rawPngStream)) {                         throw new RuntimeException(                             "This Java environment does not support converting to PNG.");                       }                     } catch (IOException exception) {                       // This should never happen because rawPngStream is an in-memory stream.                      System.out.println("IOException=" + exception);                     }                 byte[] rawPngBytes = rawPngStream.toByteArray();                 String base64Png = new Base64Encoder().encode(rawPngBytes);                                  File screenshot = OutputType.FILE.convertFromBase64Png(base64Png);                 System.out.println("screenshot==" + screenshot.toString());                 screenshot.renameTo(new File("C:\\screenshottemp.png"));                          } catch (IOException e) {             // TODO Auto-generated catch block             e.printStackTrace();             System.out.println(e);         }     }               public static void convertToRgba32(DataInput frameBuffer, int[] into) {         try {             for (int x = 0; x < into.length; x++) {                 try{                 int rgb = frameBuffer.readShort() & 0xffff;                 int red = rgb >> 11;                 red = (red << 3) | (red >> 2);                 int green = (rgb >> 5) & 63;                 green = (green << 2) | (green >> 4);                 int blue = rgb & 31;                 blue = (blue << 3) | (blue >> 2);                 into[x] = 0xff000000 | (red << 16) | (green << 8) | blue;                 }catch (EOFException e){                     System.out.println("EOFException=" + e);                 }               }         } catch (IOException exception) {             System.out.println("convertToRgba32Exception=" + exception);       }     }      } (2) 首先是直接移植SystemUI的代码,实现截图效果,这部分的代码就不贴出来了,直接去下载代码吧, 关键的代码没有几句,最最主要的是:Surface.screenshot(),请看代码吧。 [java] <SPAN style="FONT-SIZE: 16px">package org.winplus.ss; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Date; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Matrix; import android.os.Bundle; import android.util.DisplayMetrics; import android.util.Log; import android.view.Display; import android.view.Surface; import android.view.WindowManager; import android.os.SystemProperties; public class SimpleScreenshotActivity extends Activity { private Display mDisplay; private WindowManager mWindowManager; private DisplayMetrics mDisplayMetrics; private Bitmap mScreenBitmap; private Matrix mDisplayMatrix; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); new Thread(new Runnable() { @Override public void run() { takeScreenshot(); } }).start(); } private float getDegreesForRotation(int value) { switch (value) { case Surface.ROTATION_90: return 360f - 90f; case Surface.ROTATION_180: return 360f - 180f; case Surface.ROTATION_270: return 360f - 270f; } return 0f; } private void takeScreenshot() { mWindowManager = (WindowManager) getSystemService(Context.WINDOW_SERVICE); mDisplay = mWindowManager.getDefaultDisplay(); mDisplayMetrics = new DisplayMetrics(); mDisplay.getRealMetrics(mDisplayMetrics); mDisplayMatrix = new Matrix(); float[] dims = { mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels }; int value = mDisplay.getRotation(); String hwRotation = SystemProperties.get("ro.sf.hwrotation", "0"); if (hwRotation.equals("270") || hwRotation.equals("90")) { value = (value + 3) % 4; } float degrees = getDegreesForRotation(value); boolean requiresRotation = (degrees > 0); if (requiresRotation) { // Get the dimensions of the device in its native orientation mDisplayMatrix.reset(); mDisplayMatrix.preRotate(-degrees); mDisplayMatrix.mapPoints(dims); dims[0] = Math.abs(dims[0]); dims[1] = Math.abs(dims[1]); } mScreenBitmap = Surface.screenshot((int) dims[0], (int) dims[1]); if (requiresRotation) { // Rotate the screenshot to the current orientation Bitmap ss = Bitmap.createBitmap(mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels, Bitmap.Config.ARGB_8888); Canvas c = new Canvas(ss); c.translate(ss.getWidth() / 2, ss.getHeight() / 2); c.rotate(degrees); c.translate(-dims[0] / 2, -dims[1] / 2); c.drawBitmap(mScreenBitmap, 0, 0, null); c.setBitmap(null); mScreenBitmap = ss; } // If we couldn't take the screenshot, notify the user if (mScreenBitmap == null) { return; } // Optimizations mScreenBitmap.setHasAlpha(false); mScreenBitmap.prepareToDraw(); try { saveBitmap(mScreenBitmap); } catch (IOException e) { System.out.println(e.getMessage()); } } public void saveBitmap(Bitmap bitmap) throws IOException { String imageDate = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss") .format(new Date(System.currentTimeMillis())); File file = new File("/mnt/sdcard/Pictures/"+imageDate+".png"); if(!file.exists()){ file.createNewFile(); } FileOutputStream out; try { out = new FileOutputStream(file); if (bitmap.compress(Bitmap.CompressFormat.PNG, 70, out)) { out.flush(); out.close(); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } } </SPAN> package org.winplus.ss; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Date; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Matrix; import android.os.Bundle; import android.util.DisplayMetrics; import android.util.Log; import android.view.Display; import android.view.Surface; import android.view.WindowManager; import android.os.SystemProperties; public class SimpleScreenshotActivity extends Activity { private Display mDisplay; private WindowManager mWindowManager; private DisplayMetrics mDisplayMetrics; private Bitmap mScreenBitmap; private Matrix mDisplayMatrix; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); new Thread(new Runnable() { @Override public void run() { takeScreenshot(); } }).start(); } private float getDegreesForRotation(int value) { switch (value) { case Surface.ROTATION_90: return 360f - 90f; case Surface.ROTATION_180: return 360f - 180f; case Surface.ROTATION_270: return 360f - 270f; } return 0f; } private void takeScreenshot() { mWindowManager = (WindowManager) getSystemService(Context.WINDOW_SERVICE); mDisplay = mWindowManager.getDefaultDisplay(); mDisplayMetrics = new DisplayMetrics(); mDisplay.getRealMetrics(mDisplayMetrics); mDisplayMatrix = new Matrix(); float[] dims = { mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels }; int value = mDisplay.getRotation(); String hwRotation = SystemProperties.get("ro.sf.hwrotation", "0"); if (hwRotation.equals("270") || hwRotation.equals("90")) { value = (value + 3) % 4; } float degrees = getDegreesForRotation(value); boolean requiresRotation = (degrees > 0); if (requiresRotation) { // Get the dimensions of the device in its native orientation mDisplayMatrix.reset(); mDisplayMatrix.preRotate(-degrees); mDisplayMatrix.mapPoints(dims); dims[0] = Math.abs(dims[0]); dims[1] = Math.abs(dims[1]); } mScreenBitmap = Surface.screenshot((int) dims[0], (int) dims[1]); if (requiresRotation) { // Rotate the screenshot to the current orientation Bitmap ss = Bitmap.createBitmap(mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels, Bitmap.Config.ARGB_8888); Canvas c = new Canvas(ss); c.translate(ss.getWidth() / 2, ss.getHeight() / 2); c.rotate(degrees); c.translate(-dims[0] / 2, -dims[1] / 2); c.drawBitmap(mScreenBitmap, 0, 0, null); c.setBitmap(null); mScreenBitmap = ss; } // If we couldn't take the screenshot, notify the user if (mScreenBitmap == null) { return; } // Optimizations mScreenBitmap.setHasAlpha(false); mScreenBitmap.prepareToDraw(); try { saveBitmap(mScreenBitmap); } catch (IOException e) { System.out.println(e.getMessage()); } } public void saveBitmap(Bitmap bitmap) throws IOException { String imageDate = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss") .format(new Date(System.currentTimeMillis())); File file = new File("/mnt/sdcard/Pictures/"+imageDate+".png"); if(!file.exists()){ file.createNewFile(); } FileOutputStream out; try { out = new FileOutputStream(file); if (bitmap.compress(Bitmap.CompressFormat.PNG, 70, out)) { out.flush(); out.close(); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } } PS:1、需要在AndroidManifest.xml中加入代码:android:sharedUserId="android.uid.system" [email protected][email protected]ipse中添加Jar文件通过编译。 3、此代码只在Android4.0中使用过,2.3的就没去做测试了。 4 利用TakeScreenShotService截图 Android手机一般都自带有手机屏幕截图的功能:在手机任何界面(当然手机要是开机点亮状态),通过按组合键,屏幕闪一下,然后咔嚓一声,截图的照片会保存到当前手机的图库中,真是一个不错的功能! 以我手头的测试手机为例,是同时按电源键+音量下键来实现截屏,苹果手机则是电源键 + HOME键,小米手机是菜单键+音量下键,而HTC一般是按住电源键再按左下角的“主页”键。那么Android源码中使用组合键是如何实现屏幕截图功能呢?前段时间由于工作的原因仔细看了一下,这两天不忙,便把相关的知识点串联起来整理一下,分下面两部分简单分析下实现流程: Android源码中对组合键的捕获。 Android源码中对按键的捕获位于文件PhoneWindowManager.java(alps\frameworks\base\policy\src\com\android\internal\policy\impl)中,这个类处理所有的键盘输入事件,其中函数interceptKeyBeforeQueueing()会对常用的按键做特殊处理。以我手头的测试机为例,是同时按电源键和音量下键来截屏,那么在这个函数中我们会看到这么两段代码: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 ....... case KeyEvent.KEYCODE_VOLUME_DOWN: case KeyEvent.KEYCODE_VOLUME_UP: case KeyEvent.KEYCODE_VOLUME_MUTE: { if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) { if (down) { if (isScreenOn && !mVolumeDownKeyTriggered && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) { mVolumeDownKeyTriggered = true; mVolumeDownKeyTime = event.getDownTime(); mVolumeDownKeyConsumedByScreenshotChord = false; cancelPendingPowerKeyAction(); interceptScreenshotChord(); } } else { mVolumeDownKeyTriggered = false; cancelPendingScreenshotChordAction(); } ...... case KeyEvent.KEYCODE_POWER: { result &= ~ACTION_PASS_TO_USER; if (down) { if (isScreenOn && !mPowerKeyTriggered && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) { mPowerKeyTriggered = true; mPowerKeyTime = event.getDownTime(); interceptScreenshotChord(); } ...... 可以看到正是在这里(响应Down事件)捕获是否按了音量下键和电源键的,而且两个地方都会进入函数interceptScreenshotChord()中,那么接下来看看这个函数干了什么工作: 1 2 3 4 5 6 7 8 9 10 11 12 13 private void interceptScreenshotChord() { if (mVolumeDownKeyTriggered && mPowerKeyTriggered && !mVolumeUpKeyTriggered) { final long now = SystemClock.uptimeMillis(); if (now <= mVolumeDownKeyTime + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS && now <= mPowerKeyTime + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS) { mVolumeDownKeyConsumedByScreenshotChord = true; cancelPendingPowerKeyAction(); mHandler.postDelayed(mScreenshotChordLongPress, ViewConfiguration.getGlobalActionKeyTimeout()); } } } 在这个函数中,用两个布尔变量判断是否同时按了音量下键和电源键后,再计算两个按键响应Down事件之间的时间差不超过150毫秒,也就认为是同时按了这两个键后,算是真正的捕获到屏幕截屏的组合键。 附言:文件PhoneWindowManager.java类是拦截键盘消息的处理类,在此类中还有对home键、返回键等好多按键的处理。 Android源码中调用屏幕截图的接口。 捕获到组合键后,我们再看看android源码中是如何调用屏幕截图的函数接口。在上面的函数interceptScreenshotChord中我们看到用handler判断长按组合键500毫秒之后,会进入如下函数: 1 2 3 4 5 private final Runnable mScreenshotChordLongPress = new Runnable() { public void run() { takeScreenshot(); } }; 在这里启动了一个线程来完成截屏的功能,接着看函数takeScreenshot(): 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 private void takeScreenshot() { synchronized (mScreenshotLock) { if (mScreenshotConnection != null) { return; } ComponentName cn = new ComponentName("com.android.systemui", "com.android.systemui.screenshot.TakeScreenshotService"); Intent intent = new Intent(); intent.setComponent(cn); ServiceConnection conn = new ServiceConnection() { @Override public void onServiceConnected(ComponentName name, IBinder service) { synchronized (mScreenshotLock) { if (mScreenshotConnection != this) { return; } Messenger messenger = new Messenger(service); Message msg = Message.obtain(null, 1); final ServiceConnection myConn = this; Handler h = new Handler(mHandler.getLooper()) { @Override public void handleMessage(Message msg) { synchronized (mScreenshotLock) { if (mScreenshotConnection == myConn) { mContext.unbindService(mScreenshotConnection); mScreenshotConnection = null; mHandler.removeCallbacks(mScreenshotTimeout); } } } }; msg.replyTo = new Messenger(h); msg.arg1 = msg.arg2 = 0; if (mStatusBar != null && mStatusBar.isVisibleLw()) msg.arg1 = 1; if (mNavigationBar != null && mNavigationBar.isVisibleLw()) msg.arg2 = 1; try { messenger.send(msg); } catch (RemoteException e) { } } } @Override public void onServiceDisconnected(ComponentName name) {} }; if (mContext.bindService(intent, conn, Context.BIND_AUTO_CREATE)) { mScreenshotConnection = conn; mHandler.postDelayed(mScreenshotTimeout, 10000); } } } 可以看到这个函数使用AIDL绑定了service服务到"com.android.systemui.screenshot.TakeScreenshotService",注意在service连接成功时,对message的msg.arg1和msg.arg2两个参数的赋值。其中在mScreenshotTimeout中对服务service做了超时处理。接着我们找到实现这个服务service的类TakeScreenshotService,看看其实现的流程: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 public class TakeScreenshotService extends Service { private static final String TAG = "TakeScreenshotService"; private static GlobalScreenshot mScreenshot; private Handler mHandler = new Handler() { @Override public void handleMessage(Message msg) { switch (msg.what) { case 1: final Messenger callback = msg.replyTo; if (mScreenshot == null) { mScreenshot = new GlobalScreenshot(TakeScreenshotService.this); } mScreenshot.takeScreenshot(new Runnable() { @Override public void run() { Message reply = Message.obtain(null, 1); try { callback.send(reply); } catch (RemoteException e) { } } }, msg.arg1 > 0, msg.arg2 > 0); } } }; @Override public IBinder onBind(Intent intent) { return new Messenger(mHandler).getBinder(); } } 在这个类中,我们主要看调用接口,用到了mScreenshot.takeScreenshot()传递了三个参数,第一个是个runnable,第二和第三个是之前message传递的两个参数msg.arg1和msg.arg2。最后我们看看这个函数takeScreenshot(),位于文件GlobalScreenshot.java中(跟之前的函数重名但是文件路径不一样): 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 /** * Takes a screenshot of the current display and shows an animation. */ void takeScreenshot(Runnable finisher, boolean statusBarVisible, boolean navBarVisible) { // We need to orient the screenshot correctly (and the Surface api seems to take screenshots // only in the natural orientation of the device :!) mDisplay.getRealMetrics(mDisplayMetrics); float[] dims = {mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels}; float degrees = getDegreesForRotation(mDisplay.getRotation()); boolean requiresRotation = (degrees > 0); if (requiresRotation) { // Get the dimensions of the device in its native orientation mDisplayMatrix.reset(); mDisplayMatrix.preRotate(-degrees); mDisplayMatrix.mapPoints(dims); dims[0] = Math.abs(dims[0]); dims[1] = Math.abs(dims[1]); } // Take the screenshot mScreenBitmap = Surface.screenshot((int) dims[0], (int) dims[1]); if (mScreenBitmap == null) { notifyScreenshotError(mContext, mNotificationManager); finisher.run(); return; } if (requiresRotation) { // Rotate the screenshot to the current orientation Bitmap ss = Bitmap.createBitmap(mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels, Bitmap.Config.ARGB_8888); Canvas c = new Canvas(ss); c.translate(ss.getWidth() / 2, ss.getHeight() / 2); c.rotate(degrees); c.translate(-dims[0] / 2, -dims[1] / 2); c.drawBitmap(mScreenBitmap, 0, 0, null); c.setBitmap(null); mScreenBitmap = ss; } // Optimizations mScreenBitmap.setHasAlpha(false); mScreenBitmap.prepareToDraw(); // Start the post-screenshot animation startAnimation(finisher, mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels, statusBarVisible, navBarVisible); } 这段代码的注释比较详细,其实看到这里,我们算是真正看到截屏的操作了,具体的工作包括对屏幕大小、旋转角度的获取,然后调用Surface类的screenshot方法截屏保存到bitmap中,之后把这部分位图填充到一个画布上,最后再启动一个延迟的拍照动画效果。如果再往下探究screenshot方法,发现已经是一个native方法了: 1 2 3 4 5 6 7 /** * Like [email protected] #screenshot(int, int, int, int)} but includes all * Surfaces in the screenshot. * * @hide */ public static native Bitmap screenshot(int width, int height); 使用JNI技术调用底层的代码,如果再往下走,会发现映射这这个jni函数在文件android_view_Surface.cpp中,这个真的已经是底层c++语言了,统一调用的底层函数是: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 static jobject doScreenshot(JNIEnv* env, jobject clazz, jint width, jint height, jint minLayer, jint maxLayer, bool allLayers) { ScreenshotPixelRef* pixels = new ScreenshotPixelRef(NULL); if (pixels->update(width, height, minLayer, maxLayer, allLayers) != NO_ERROR) { delete pixels; return 0; } uint32_t w = pixels->getWidth(); uint32_t h = pixels->getHeight(); uint32_t s = pixels->getStride(); uint32_t f = pixels->getFormat(); ssize_t bpr = s * android::bytesPerPixel(f); SkBitmap* bitmap = new SkBitmap(); bitmap->setConfig(convertPixelFormat(f), w, h, bpr); if (f == PIXEL_FORMAT_RGBX_8888) { bitmap->setIsOpaque(true); } if (w > 0 && h > 0) { bitmap->setPixelRef(pixels)->unref(); bitmap->lockPixels(); } else { // be safe with an empty bitmap. delete pixels; bitmap->setPixels(NULL); } return GraphicsJNI::createBitmap(env, bitmap, false, NULL); } 由于对C++不熟,我这里就不敢多言了。其实到这里,算是对手机android源码中通过组合键屏幕截图的整个流程有个大体了解了,一般我们在改动中熟悉按键的捕获原理,并且清楚调用的截屏函数接口即可,如果有兴趣的,可以继续探究更深的底层是如何实现的。 应用

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