android 开发矩形截屏插件,Android 上如何实现矩形区域截屏

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：

在屏幕上标出截图的矩形区域

调用系统接口截屏

对截图进行裁剪

效果图如下：

矩形区域截屏

***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：

手指拖动形成矩形区域;

可以拖动已经划好的矩形区域进行移动;

可以拖动矩形区域的边框调整大小;

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：

publicclass ScreenCaptureActivity extends Activity { privatestaticfinal String TAG = ScreenCaptureActivity.class.getName(); private MediaProjectionManager mMediaProjectionManager; privateintREQUEST_MEDIA_PROJECTION = 1; private SimpleDateFormat dateFormat; private String pathImage; private WindowManager mWindowManager; private ImageReader mImageReader; private MediaProjection mMediaProjection; privateintmResultCode; private Intent mResultData; private VirtualDisplay mVirtualDisplay; private String strDate; privateintwindowWidth; privateintwindowHeight; private String nameImage; privateintmScreenDensity; @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

publicvoid onActivityResult(intrequestCode,intresultCode, Intent data) { if (requestCode == REQUEST_MEDIA_PROJECTION) { if (resultCode != Activity.RESULT_OK) {return;

} elseif (data !=null&& resultCode != 0) {

mResultCode = resultCode;

mResultData = data;

startVirtual(); new Handler(Looper.getMainLooper()).postDelayed(new Runnable() { @Override

publicvoid 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) publicvoid 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) publicvoid 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(); intwidth = image.getWidth();intheight = image.getHeight(); final Image.Plane[] planes = image.getPlanes(); final ByteBuffer buffer = planes[0].getBuffer();intpixelStride = planes[0].getPixelStride();introwStride = planes[0].getRowStride();introwPadding = 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");

}

第三步、对截图进行裁剪

根据***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：

if (mRect !=null) { if (mRect.left

mRect.left= 0; if (mRect.right

mRect.right= 0; if (mRect.top

mRect.top= 0; if (mRect.bottom

mRect.bottom = 0; intcut_width = Math.abs(mRect.left- mRect.right);intcut_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);

}

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 Android如何判断NavigationBar是否显示(获取屏幕真实的高度) 。

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：