Android实现矩形区域截屏的方法

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。

晚截图可以分成三步：

1. 在屏幕上标出截图的矩形区域

2. 调用系统接口截屏

3. 对截图进行裁剪

效果图如下：

第一步、在屏幕上标识出截图区域

首先确定标识截图区域所需要的功能：

1. 手指拖动形成矩形区域；

2. 可以拖动已经划好的矩形区域进行移动；

3. 可以拖动矩形区域的边框调整大小；

4. 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。

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Bigbang项目的MarkSizeView类。

第二步、调用系统接口截屏

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。

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。

直接看代码：

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");
 }
} 

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