今天在使用OpenCV Library 2.4.10建立了我的第一個基於opencv的Android程式，先貼出我的程式碼：

package com.example.facedetector;

import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewFrame;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewListener2;
import org.opencv.android.LoaderCallbackInterface;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.core.MatOfRect;
import org.opencv.core.Point;
import org.opencv.core.Rect;
import org.opencv.core.Scalar;
import org.opencv.highgui.Highgui;
import org.opencv.imgproc.Imgproc;
import org.opencv.objdetect.CascadeClassifier;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.SurfaceView;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity implements CvCameraViewListener2, OnClickListener {

	private Button btnStart;
	private CameraBridgeViewBase cameraPreview = null; 
	private Mat mRgba; 
	private boolean startProcess = false;
	protected BaseLoaderCallback  mLoaderCallback = new BaseLoaderCallback(this) {
		@Override
		public void onManagerConnected(int status) {
			switch (status) {
			case LoaderCallbackInterface.SUCCESS:
			{
				cameraPreview.enableView();
			} break;
			default:
			{
				super.onManagerConnected(status);
			} break;
			}
		}
	};

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		cameraPreview = (CameraBridgeViewBase) findViewById(R.id.cameraView);
		cameraPreview.setVisibility(SurfaceView.VISIBLE);
		cameraPreview.setCvCameraViewListener(this);

		btnStart = (Button) findViewById(R.id.btnStart);
		btnStart.setOnClickListener(this);

	}
	
	@Override
	protected void onResume() {
		super.onResume();
	<strong>	OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_2_4_10, getApplicationContext(), mLoaderCallback );</strong>
	}


	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// Handle action bar item clicks here. The action bar will
		// automatically handle clicks on the Home/Up button, so long
		// as you specify a parent activity in AndroidManifest.xml.
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}

	private void startFaceDetetion(Mat image){
		String xmlfilePath=getClass().getResource("lbpcascade_frontalface.xml").getPath().substring(1);  
		CascadeClassifier faceDetector = new CascadeClassifier(xmlfilePath);  
		// Detect faces in the image.  
		// MatOfRect is a special container class for Rect.  
		MatOfRect faceDetections = new MatOfRect();  
		faceDetector.detectMultiScale(image, faceDetections);  

		System.out.println(String.format("Detected %s faces", faceDetections.toArray().length));  

		// Draw a bounding box around each face.  
		for (Rect rect : faceDetections.toArray()) {  
			Scalar color = new Scalar(0, 255, 0);
			Core.rectangle(image, new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height), color);
		} 

	}

	@Override
	protected void onDestroy() {
		super.onDestroy();
        if (cameraPreview != null) {
        	cameraPreview.disableView();
        	startProcess = false;
        }
	}

	@Override
	protected void onPause() {
		super.onPause();
		if(cameraPreview != null){
			cameraPreview.disableView();
			startProcess = false;
		}
	}

	@Override
	public void onCameraViewStarted(int width, int height) {
		mRgba =  new Mat(height, width, CvType.CV_8UC4);	
	}

	@Override
	public void onCameraViewStopped() {
		mRgba.release();
	}

	@Override
	public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
	    if(startProcess == true)
		{
	    	mRgba = inputFrame.rgba();
 

                return mRgba
	    }
	    return null;
	}

	@Override
	public void onClick(View v) {
		startProcess = !startProcess;
	}
}

08-18 20:57:03.549: E/AndroidRuntime(3444): java.lang.RuntimeException: Unable to resume activity {com.example.facedetector/com.example.facedetector.MainActivity}: java.lang.IllegalArgumentException: Service Intent must be explicit: Intent { act=org.opencv.engine.BIND }
 

網路上也有人遇到了同樣的問題，給出的解決方案是：

Try using getApplicationContext() instead of this in OpenCVLoader.initAsync(..)

但是我在修改後，程式依然無法執行。

出現上述問題的原因主要是因為使用了Android 5.0作為targetsdk，專業的解釋 in here。這裡我就不多說，大家可以自行研究。簡單解釋是：

Android 5.0 service intents must be explicit intents and the OpenCV library uses implicit intents in the
AsyncServiceHelper.java ( new Intent("org.opencv.engine.BIND") ), so it doesn't work.

既然是因為SDK version 的問題，那麼只需要改變version就可以了，因此這裡我將我的targetsdk由API 21改為了API 19：

android:targetSdkVersion="21"  --------->  android:targetSdkVersion="19"

問題解決了，這時候就可以正常執行APP了。