android 些许记录

Android 计时器的使用

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mTT = new TimerTask() {
				@Override
				public void run() {
					Message msg = myHandler.obtainMessage();
					msg.what = MESSAGE_SENDTO_SERVER;
					myHandler.sendMessage(msg);
				}
			};
			mTimer.scheduleAtFixedRate(mTT, 1, 4000);
  • TimerTask 后面加要在计时器中todo的事情
  • public void scheduleAtFixedRate(TimerTask task,
    Date firstTime,
long period)
  • task - task to be scheduled.
    firstTime - First time at which task is to be executed.
    period - time in milliseconds between successive task executions.

Android 摄像机预览图片上传服务器

图片处理

  • 在Camera.PreviewCallback方法中处理
  • 用YuvImage 获取图片和转化为jpg
  • 用Matrix 和 Bitmap 对图片进行高效处理
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    private Camera.PreviewCallback mPreviewCallback = new Camera.PreviewCallback() {

    		@Override
    		public void onPreviewFrame(byte[] data, Camera camera) {

    			if (!mNeedToSend) {
    				return;
    			}
    			mNeedToSend = false;

    			Camera.Parameters parameters = camera.getParameters();

    			// Log.d(TAG, "frame updated...........:" + data.length);
    			Log.d(TAG, "Data sends to the server!");
    			try {
    				YuvImage yuvImage = new YuvImage(data,
    						parameters.getPreviewFormat(),
    						parameters.getPreviewSize().width,
    						parameters.getPreviewSize().height, null);
    				ByteArrayOutputStream baos = new ByteArrayOutputStream();
    				yuvImage.compressToJpeg(
    						new Rect(0, 0, parameters.getPreviewSize().width,
    								parameters.getPreviewSize().height), 90,
    						baos);
    				yuvImage = null;

    				byte cdata[] = baos.toByteArray();
    				Bitmap bitmap = BitmapFactory.decodeByteArray(cdata, 0,
    						cdata.length);
    				baos.close();
    				baos = null;

    				Matrix matrix = new Matrix();
    				matrix.postRotate(-90);
    				matrix.postScale(-1, -1);
    				Bitmap rBitmap = Bitmap
    						.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
    								bitmap.getHeight(), matrix, true);
    				bitmap.recycle();
    				bitmap = null;

    				int w = 252;
    				int h = 336;
    				float scaleWidth = ((float) w) / rBitmap.getWidth();
    				float scaleHeight = ((float) h) / rBitmap.getHeight();

    				Matrix matrix2 = new Matrix();
    				matrix2.postScale(scaleWidth, scaleHeight);
    				Bitmap rrrBitmap = Bitmap.createBitmap(rBitmap, 0, 0,
    						rBitmap.getWidth(), rBitmap.getHeight(), matrix2, true);
    				Log.d(TAG,
    						"(" + rrrBitmap.getWidth() + ","
    								+ rrrBitmap.getHeight() + ")");
    				rBitmap.recycle();
    				rBitmap = null;

    				if (null != rrrBitmap) {

    					ByteArrayOutputStream rbaos = new ByteArrayOutputStream();
    					//带缓冲区的输出流，能够提高文件的写入效率
    					BufferedOutputStream bos = new BufferedOutputStream(rbaos);
    					rrrBitmap.compress(Bitmap.CompressFormat.JPEG, 80, bos);

    					bos.flush();
    					bos.close();
    					// Send Data to server.
    					sendJpeg2Server(rbaos.toByteArray());
    					rbaos.close();
    					rrrBitmap.recycle();
    					rrrBitmap = null;
    				}

    			} catch (FileNotFoundException e) {
    				e.printStackTrace();
    			} catch (IOException e) {
    				e.printStackTrace();
    			} finally {
    			}

    		}