Android 上如何实现矩形区域截屏

   <p>对屏幕进行截屏并裁剪有两种方式：早截图和晚截图。早截图，就是先截取全屏，再让用户对截取到的图片进行修改；与之相对的，晚截图，就是先让用户在屏幕上划好区域，再进行截图和裁剪。其实两者并没有什么太大的区别，这篇就说说怎么实现晚截图。</p>    <p>晚截图可以分成三步：</p>    <ol>     <li>在屏幕上标出截图的矩形区域</li>     <li>调用系统接口截屏</li>     <li>对截图进行裁剪</li>    </ol>    <p>效果图如下：</p>    <p><img src="https://simg.open-open.com/show/b4c8b75c11073851ccb6436462d27636.gif"></p>    <p>矩形区域截屏</p>    <h3>第一步、在屏幕上标识出截图区域</h3>    <p>首先确定标识截图区域所需要的功能：</p>    <ol>     <li>手指拖动形成矩形区域；</li>     <li>可以拖动已经划好的矩形区域进行移动；</li>     <li>可以拖动矩形区域的边框调整大小；</li>     <li>选择完成以后，有“确认”和“取消”功能，“确认”时可以获得选取的区域位置。需要注意的是，按钮的位置应该能够自适应，比如选框几乎占据全屏的情况下，应该把按钮放到选框内部。</li>    </ol>    <p>最简单的方式就是写一个自定义View，根据touch的位置执行不同的功能即可。实现很简单，只要细心把每一种状态就行，代码请看 <a href="/misc/goto?guid=4959733700474291298" rel="nofollow,noindex">Bigbang</a> 项目的MarkSizeView类。</p>    <h3>第二步、调用系统接口截屏</h3>    <p>截屏必须在Activity中进行，因为需要调用startActivityForResult()。不过也可以把mMediaProjectionManager传到service中进行后续处理。</p>    <p>还要注意的是Activity本身在截屏的时候应该是透明的，不能对要截取得内容有影响。</p>    <p>直接看代码：</p>    <pre>  <code class="language-java">public class ScreenCaptureActivity extends Activity {      private static final String TAG = ScreenCaptureActivity.class.getName();      private MediaProjectionManager mMediaProjectionManager;      private int REQUEST_MEDIA_PROJECTION = 1;      private SimpleDateFormat dateFormat;      private String pathImage;      private WindowManager mWindowManager;      private ImageReader mImageReader;      private MediaProjection mMediaProjection;      private int mResultCode;      private Intent mResultData;      private VirtualDisplay mVirtualDisplay;      private String strDate;      private int windowWidth;      private int windowHeight;      private String nameImage;      private int mScreenDensity;        @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)      @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          mMediaProjectionManager = (MediaProjectionManager) getApplication().getSystemService(Context.MEDIA_PROJECTION_SERVICE);          createVirtualEnvironment();          startActivityForResult(mMediaProjectionManager.createScreenCaptureIntent(), REQUEST_MEDIA_PROJECTION);      }        @TargetApi(Build.VERSION_CODES.LOLLIPOP)      @Override      public void onActivityResult(int requestCode, int resultCode, Intent data) {          if (requestCode == REQUEST_MEDIA_PROJECTION) {              if (resultCode != Activity.RESULT_OK) {                  return;              } else if (data != null && resultCode != 0) {                  mResultCode = resultCode;                  mResultData = data;                    startVirtual();                  new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {                      @Override                      public void run() {                          startCapture();                      }                  },100);              }          }      }        @RequiresApi(api = Build.VERSION_CODES.KITKAT)      private void createVirtualEnvironment() {          dateFormat = new SimpleDateFormat("yyyy_MM_dd_hh_mm_ss");          strDate = dateFormat.format(new Date());          pathImage = Environment.getExternalStorageDirectory().getPath() + "/Pictures/";          nameImage = pathImage + strDate + ".png";          mMediaProjectionManager = (MediaProjectionManager) getApplication().getSystemService(Context.MEDIA_PROJECTION_SERVICE);          mWindowManager = (WindowManager) getApplication().getSystemService(Context.WINDOW_SERVICE);          windowWidth = mWindowManager.getDefaultDisplay().getWidth();          windowHeight = mWindowManager.getDefaultDisplay().getHeight();          DisplayMetrics metrics = new DisplayMetrics();          mWindowManager.getDefaultDisplay().getMetrics(metrics);          mScreenDensity = metrics.densityDpi;          mImageReader = ImageReader.newInstance(windowWidth, windowHeight, 0x1, 2); //ImageFormat.RGB_565            Log.i(TAG, "prepared the virtual environment");      }        @TargetApi(Build.VERSION_CODES.LOLLIPOP)      public void startVirtual() {          if (mMediaProjection != null) {              Log.i(TAG, "want to display virtual");              virtualDisplay();          } else {              Log.i(TAG, "start screen capture intent");              Log.i(TAG, "want to build mediaprojection and display virtual");              setUpMediaProjection();              virtualDisplay();          }      }        @TargetApi(Build.VERSION_CODES.LOLLIPOP)      public void setUpMediaProjection() {          mMediaProjection = mMediaProjectionManager.getMediaProjection(mResultCode, mResultData);          Log.i(TAG, "mMediaProjection defined");      }        @TargetApi(Build.VERSION_CODES.LOLLIPOP)      private void virtualDisplay() {          mVirtualDisplay = mMediaProjection.createVirtualDisplay("screen-mirror",                  windowWidth, windowHeight, mScreenDensity, DisplayManager.VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR,                  mImageReader.getSurface(), null, null);          Log.i(TAG, "virtual displayed");      }        @TargetApi(Build.VERSION_CODES.LOLLIPOP)      private void startCapture() {          strDate = dateFormat.format(new java.util.Date());          nameImage = pathImage + strDate + ".png";            Image image = mImageReader.acquireLatestImage();          int width = image.getWidth();          int height = image.getHeight();          final Image.Plane[] planes = image.getPlanes();          final ByteBuffer buffer = planes[0].getBuffer();          int pixelStride = planes[0].getPixelStride();          int rowStride = planes[0].getRowStride();          int rowPadding = rowStride - pixelStride * width;          Bitmap bitmap = Bitmap.createBitmap(width + rowPadding / pixelStride, height, Bitmap.Config.ARGB_8888);          bitmap.copyPixelsFromBuffer(buffer);          bitmap = Bitmap.createBitmap(bitmap, 0, 0, width, height);          image.close();          Log.i(TAG, "image data captured");            //保存截屏结果，如果要裁剪图片，在这里处理bitmap          if (bitmap != null) {              try {                  File fileImage = new File(nameImage);                  if (!fileImage.exists()) {                      fileImage.createNewFile();                      Log.i(TAG, "image file created");                  }                  FileOutputStream out = new FileOutputStream(fileImage);                  if (out != null) {                      bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);                      out.flush();                      out.close();                      Intent media = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);                      Uri contentUri = Uri.fromFile(fileImage);                      media.setData(contentUri);                      this.sendBroadcast(media);                      Log.i(TAG, "screen image saved");                  }              } catch (FileNotFoundException e) {                  e.printStackTrace();              } catch (IOException e) {                  e.printStackTrace();              }          }      }        @TargetApi(Build.VERSION_CODES.LOLLIPOP)      private void tearDownMediaProjection() {          if (mMediaProjection != null) {              mMediaProjection.stop();              mMediaProjection = null;          }          Log.i(TAG, "mMediaProjection undefined");      }  }</code></pre>    <h3>第三步、对截图进行裁剪</h3>    <p>根据第一步得到的截图区域mRect对第二步中得到的截屏结果bitmap进行裁剪：</p>    <pre>  <code class="language-java">if (mRect != null) {      if (mRect.left < 0)          mRect.left = 0;      if (mRect.right < 0)          mRect.right = 0;      if (mRect.top < 0)          mRect.top = 0;      if (mRect.bottom < 0)          mRect.bottom = 0;      int cut_width = Math.abs(mRect.left - mRect.right);      int cut_height = Math.abs(mRect.top - mRect.bottom);      if (cut_width > 0 && cut_height > 0) {      Bitmap cutBitmap = Bitmap.createBitmap(bitmap, mRect.left, mRect.top, cut_width, cut_height);  }</code></pre>    <p>需要注意的是，在调用系统截屏功能的时候，如果手机有NavigationBar（虚拟导航栏），windowHeight的取值就是不包括NavigationBar的高度的，如果不进行调整，就会导致截屏被压缩。如何获取屏幕的真实高度，可以参考 <a href="/misc/goto?guid=4959733700562646558" rel="nofollow,noindex">Android如何判断NavigationBar是否显示（获取屏幕真实的高度）</a> 。</p>    <p>而且NavigationBar还会导致截屏的结果出现边框，边框的颜色是透明的，原因是第二步代码中的rowPadding！=0，截屏如下图所示：</p>    <p><img src="https://simg.open-open.com/show/729c24e55067610e78f2102d96ee611a.png"></p>    <p>带NavigationBar使用系统截图的结果</p>    <p>那么如果我们想要对截图的结果进行保存或者裁剪，就必须要去除边框，找出真正的内容区域，也就是在第一个不透明的像素和最后一个不透明像素之间的内容，然后才能对得到的区域进行第三步的裁剪，代码如下：</p>    <pre>  <code class="language-java">int[] pixel=new int[width];  bitmap.getPixels(pixel,0,width ,0,0,width,1);  int leftPadding=0;  int rightPadding=width;  for (int i=0;i<pixel.length;i++){      if (pixel[i]!=0){          leftPadding=i;          break;      }  }  for (int i=pixel.length-1;i>=0;i--){      if (pixel[i]!=0){          rightPadding=i;          break;      }  }  bitmap=Bitmap.createBitmap(bitmap,leftPadding, 0, rightPadding-leftPadding, height);</code></pre>    <p>处理后的截图如下：</p>    <p><img src="https://simg.open-open.com/show/81dc38494be809cf4641d8cfe8eb332f.png"></p>    <p>取得截图结果的内容部分</p>    <p>你可能会觉得既然是rowPadding！=0导致出现边框，而且边框只在右边，为什么不直接把右边rowPadding宽度的内容截掉呢？其实是因为如果不调整windowHeight，就会在左边也产生框，所以才用了上面的方法。</p>    <p>完整代码可以参考 <a href="/misc/goto?guid=4959733700474291298" rel="nofollow,noindex">Bigbang</a> 项目的MarkSizeView类、ScreenCaptureActivity类和ScreenCapture类。</p>    <p> </p>    <p>来自：http://www.jianshu.com/p/0462dae4c808</p>    <p> </p>