Android调用摄像头（二）

第六步，我们必须对按键事件进行监听，如是拍照还是聚焦，代码如下

public boolean onKeyDown(intkeyCode, KeyEvent event) {//处理按键事件
if(camera!=null&&event.getRepeatCount()==0)//代表只按了一下
{
switch(keyCode){
caseKeyEvent.KEYCODE_BACK://如果是搜索键
          camera.autoFocus(null);//自动对焦
    break;
      caseKeyEvent.KEYCODE_DPAD_CENTER://如果是中间键
          camera.takePicture(null,null, newTakePictureCallback());//将拍到的照片给第三个对象中，这里的TakePictureCallback()是自己定义的，在下面的代码中
  break;
}
}
returntrue;//阻止事件往下传递，否则按搜索键会变成系统默认的
}
------------------------------------------------------------------------------------------
private final classTakePictureCallback implements PictureCallback{
public void onPictureTaken(byte[]data, Camera camera) {
try {
Bitmap bitmap =BitmapFactory.decodeByteArray(data, 0, data.length);
File file = newFile(Environment.getExternalStorageDirect ory(),System.currentTimeMillis()+".jpg");
FileOutputStream outputStream = newFileOutputStream(file);
bitmap.compress(CompressFormat.JPEG,100, outputStream);
outputStream.close();
camera.stopPreview();
camera.startPreview();//处理完数据之后可以预览
} catch (Exception e) {
Log.e(TAG, e.toString());
}
}
}

注意，代码中有两个回调类，一个是SurfaceCallback(),另外一个是TakePictureCallback()，初学者可能一时难以理解，通俗地讲，前者是用来监视surficeView这个暂时存放图片数据的显示控件的，根据它的显示情况调用不同的方法，包括surfaceCreated(),surfaceChanged(),surfaceDestroyed(),也就不难理解为什么会有这三个回调方法了(注意，在surfaceDestroyed（）方法中必须释放摄像头，详细代码参见上方)。TakePictureCallback()是为了监视是否拍照而设计的接口，期中也仅有一个方法，camera将拍照得到的数据传入方法，我们便可以对拍照得到的数据进行进一步处理了。

至此，简单的拍照功能介绍完毕！

packagecn.camera.rxm;
 
importjava.io.File;
importjava.io.FileOutputStream;
importjava.io.IOException;
importjava.util.Calendar;
importjava.util.Locale;
 
importorg.apache.commons.logging.Log;
 
importandroid.text.format.DateFormat;
importandroid.util.*;
importandroid.app.Activity;
importandroid.content.Context;
importandroid.graphics.Bitmap;
importandroid.graphics.Bitmap.CompressFormat;
importandroid.graphics.BitmapFactory;
importandroid.graphics.PixelFormat;
importandroid.hardware.Camera;
importandroid.hardware.Camera.PictureCallback;
importandroid.os.Bundle;
importandroid.os.Environment;
importandroid.view.LayoutInflater;
importandroid.view.Menu;
importandroid.view.MenuItem;
importandroid.view.SurfaceHolder;
importandroid.view.SurfaceView;
importandroid.view.View;
importandroid.view.View.OnClickListener;
importandroid.widget.Button;
//importandroid.widget.Toast;
 
 
 
 
public classMycamActivity extends Activity {
   
privatePreview mPreview;
privateCamera mCamera;
BitmapCameraBitmap;
SurfaceHolder mHolder;
privatestatic final int OPTION_SNAPSHOT = 0;
privatestatic final int OPTION_STOPCAMERA = 1;
private ViewviewStart;
    @Override
     
     
    public void onCreate(BundlesavedInstanceState) {
        super.onCreate(savedInstanceState);
        LayoutInflater flater =this.getLayoutInflater();
        viewStart = flater.inflate(R.layout.main,null);
        setContentView(viewStart);
         
        Button btn1 =(Button)findViewById(R.id.button1);
         
        btn1.setOnClickListener(
        new OnClickListener(){
        public void onClick(View v){
       
        mPreview = new Preview(getBaseContext());
        setContentView(mPreview); 
        };
        }
        );
    }
     
     
    public booleanonCreateOptionsMenu(Menu menu){
//
menu.add(0,OPTION_SNAPSHOT, 0, R.string.take);
//
menu.add(0,OPTION_STOPCAMERA, 1, R.string.back);
//
returntrue;//super.onCreateOptionsMenu(menu);
}
publicboolean onOptionsItemSelected(MenuItem item) {
//
 
int itemId =item.getItemId();
//
switch(itemId){
caseOPTION_SNAPSHOT:
//拍摄照片
mCamera.takePicture(null, null, jpegCallback);
try {
Thread.sleep(4000);
} catch(InterruptedException e) {
// TODOAuto-generated catch block
e.printStackTrace();
}
mCamera.startPreview();
break;
caseOPTION_STOPCAMERA:
 
mPreview =null;  
setContentView(viewStart); 
break;
}
 
returntrue;
}
privatePictureCallback jpegCallback = new PictureCallback(){
 
//
public voidonPictureTaken(byte[] data, Camera camera) {
 
try {
String name = newDateFormat().format("yyyyMMdd_hhmmss",
Calendar.getInstance(Locale.CHINA)) +".jpg";
FileOutputStream fileout = newFileOutputStream("/mnt/sdcard/sdcard/DCIM/"+ name);
System.out.println(name);
fileout.write(data,0,data.length);
fileout.flush();
fileout.close();
} catch (IOException e) {
// TODO: handle exception
System.out.println(e);
}
 
}
};
classPreview extends SurfaceView implements SurfaceHolder.Callback
{
Preview(Context context)
{
super(context);
mHolder=getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public voidsurfaceCreated(SurfaceHolder holder)
{
mCamera=Camera.open();
try
{
mCamera.setPreviewDisplay(holder);
}
catch(IOException exception)
{
mCamera.release();
mCamera=null;
}
}
public voidsurfaceDestroyed(SurfaceHolder holder)
{
mCamera.stopPreview();
mCamera.release();
}
 
 
@Override
public voidsurfaceChanged(SurfaceHolder holder, int format, int w, int h){
// TODOAuto-generated method stub
Camera.Parameters parameters=mCamera.getParameters();
parameters.setPictureFormat(PixelFormat.JPEG);
parameters.setPreviewSize(1024, 1024);
 
mCamera.setParameters(parameters);
mCamera.setDisplayOrientation(90);
mCamera.startPreview();
}
}
}