玩转Android Camera开发(2):使用TextureView和SurfaceTexture预览Camera 基础拍照demo

Google自Android4.0出了TextureView，为什么推出呢？就是为了弥补Surfaceview的不足，另外一方面也是为了平衡GlSurfaceView，当然这是本人揣度的。关于TextureView、Surfaceview、SurfaceTexture、GLSurfaceView的关系，待咱家推出GLSurfaceview预览Camera后再专门分析。本文主要介绍使用TextureView预览Camera。

其实关于如何用TextureView预览Camera，官网已经给出了demo，参见这里。另外，链接1 链接2也给出了完整的预览Camera的demo，但都是一堆东西染在一块。本文就利用前文 搭建的一个轻量级的Camera框架来快速替换掉Surfaceview。因为用Surfaceview预览的话传一个SurfaceHolder进去，用Textureview预览的话需要传进去一个SurfaceTexture。其他的Camera流程不变。

一、新建CameraTextureView类继承TextureView，并实现TextureView.SurfaceTextureListener接口。实现这个接口就像实现SurfaceHolder.Callback，最主要的目的是在SurfaceTexture准备好后能够知道，也即onSurfaceTextureAvailable这个函数。

CameraTextureView.java

package org.yanzi.camera.preview;import org.yanzi.camera.CameraInterface;import android.content.Context;import android.graphics.PixelFormat;import android.graphics.SurfaceTexture;import android.util.AttributeSet;import android.util.Log;import android.view.SurfaceHolder;import android.view.SurfaceView;import android.view.TextureView;public class CameraTextureView extends TextureView implements TextureView.SurfaceTextureListener {	private static final String TAG = "yanzi";	Context mContext;	SurfaceTexture mSurface;	public CameraTextureView(Context context, AttributeSet attrs) {		super(context, attrs);		// TODO Auto-generated constructor stub		mContext = context;		this.setSurfaceTextureListener(this);	}	@Override	public void onSurfaceTextureAvailable(SurfaceTexture surface, int width,			int height) {		// TODO Auto-generated method stub		Log.i(TAG, "onSurfaceTextureAvailable...");		mSurface = surface;//		CameraInterface.getInstance().doStartPreview(surface, 1.33f);	}	@Override	public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {		// TODO Auto-generated method stub		Log.i(TAG, "onSurfaceTextureDestroyed...");		CameraInterface.getInstance().doStopCamera();		return true;	}	@Override	public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width,			int height) {		// TODO Auto-generated method stub		Log.i(TAG, "onSurfaceTextureSizeChanged...");	}	@Override	public void onSurfaceTextureUpdated(SurfaceTexture surface) {		// TODO Auto-generated method stub		Log.i(TAG, "onSurfaceTextureUpdated...");			}		/* 让Activity能得到TextureView的SurfaceTexture	 * @see android.view.TextureView#getSurfaceTexture()	 */	public SurfaceTexture _getSurfaceTexture(){		return mSurface;	}}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context=".CameraActivity" >    <FrameLayout        android:layout_width="wrap_content"        android:layout_height="wrap_content" >        <org.yanzi.camera.preview.CameraTextureView            android:id="@+id/camera_textureview"            android:layout_width="0dip"            android:layout_height="0dip" />    </FrameLayout>    <ImageButton        android:id="@+id/btn_shutter"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:background="@drawable/btn_shutter_background"        android:layout_alignParentBottom="true"        android:layout_centerHorizontal="true"         android:layout_marginBottom="10dip"/></RelativeLayout>

/**使用Surfaceview开启预览	 * @param holder	 * @param previewRate	 */	public void doStartPreview(SurfaceHolder holder, float previewRate){		Log.i(TAG, "doStartPreview...");		if(isPreviewing){			mCamera.stopPreview();			return;		}		if(mCamera != null){			try {				mCamera.setPreviewDisplay(holder);			} catch (IOException e) {				// TODO Auto-generated catch block				e.printStackTrace();			}			initCamera(previewRate);		}	}	/**使用TextureView预览Camera	 * @param surface	 * @param previewRate	 */	public void doStartPreview(SurfaceTexture surface, float previewRate){		Log.i(TAG, "doStartPreview...");		if(isPreviewing){			mCamera.stopPreview();			return;		}		if(mCamera != null){			try {				mCamera.setPreviewTexture(surface);			} catch (IOException e) {				// TODO Auto-generated catch block				e.printStackTrace();			}			initCamera(previewRate);		}			}

	private void initCamera(float previewRate){		if(mCamera != null){			mParams = mCamera.getParameters();			mParams.setPictureFormat(PixelFormat.JPEG);//设置拍照后存储的图片格式//			CamParaUtil.getInstance().printSupportPictureSize(mParams);//			CamParaUtil.getInstance().printSupportPreviewSize(mParams);			//设置PreviewSize和PictureSize			Size pictureSize = CamParaUtil.getInstance().getPropPictureSize(					mParams.getSupportedPictureSizes(),previewRate, 800);			mParams.setPictureSize(pictureSize.width, pictureSize.height);			Size previewSize = CamParaUtil.getInstance().getPropPreviewSize(					mParams.getSupportedPreviewSizes(), previewRate, 800);			mParams.setPreviewSize(previewSize.width, previewSize.height);			mCamera.setDisplayOrientation(90);//			CamParaUtil.getInstance().printSupportFocusMode(mParams);			List<String> focusModes = mParams.getSupportedFocusModes();			if(focusModes.contains("continuous-video")){				mParams.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);			}			mCamera.setParameters(mParams);				mCamera.startPreview();//开启预览			isPreviewing = true;			mPreviwRate = previewRate;			mParams = mCamera.getParameters(); //重新get一次			Log.i(TAG, "最终设置:PreviewSize--With = " + mParams.getPreviewSize().width					+ "Height = " + mParams.getPreviewSize().height);			Log.i(TAG, "最终设置:PictureSize--With = " + mParams.getPictureSize().width					+ "Height = " + mParams.getPictureSize().height);		}	}

		Thread openThread = new Thread(){			@Override			public void run() {				// TODO Auto-generated method stub				CameraInterface.getInstance().doOpenCamera(CameraActivity.this);			}		};		openThread.start();

	@Override	public void cameraHasOpened() {		// TODO Auto-generated method stub		SurfaceTexture surface = textureView._getSurfaceTexture();		CameraInterface.getInstance().doStartPreview(surface, previewRate);	}

几个注意事项:

1、TextureView是Android 4.0之后加入的，低版本么这个类。TextureView必须工作在开启硬件加速的环境中，也即配置文件里Activity的设置项里：android:hardwareAccelerated="true" 默认的这个属性就是true，因此不用再写了。但如果写成false，可以看到onSurfaceTextureAvailable()这个回调就进不来了，TextureView没有了SurfaceTexture还玩个屁啊。

2、本文demo打开camera并预览的正常log是:

	Line 417: 06-22 12:37:43.682 I/yanzi   ( 4917): Camera open....	Line 489: 06-22 12:37:43.758 I/yanzi   ( 4917): onSurfaceTextureAvailable...	Line 533: 06-22 12:37:43.819 I/yanzi   ( 4917): Camera open over....	Line 535: 06-22 12:37:43.819 I/yanzi   ( 4917): doStartPreview...	Line 537: 06-22 12:37:43.825 I/yanzi   ( 4917): PictureSize : w = 1280h = 720	Line 539: 06-22 12:37:43.825 I/yanzi   ( 4917): PreviewSize:w = 800h = 448	Line 555: 06-22 12:37:43.874 I/yanzi   ( 4917): 最终设置:PreviewSize--With = 800Height = 448	Line 557: 06-22 12:37:43.874 I/yanzi   ( 4917): 最终设置:PictureSize--With = 1280Height = 720	Line 577: 06-22 12:37:44.106 I/yanzi   ( 4917): onSurfaceTextureUpdated...	Line 579: 06-22 12:37:44.138 I/yanzi   ( 4917): onSurfaceTextureUpdated...	Line 583: 06-22 12:37:44.169 I/yanzi   ( 4917): onSurfaceTextureUpdated...	Line 585: 06-22 12:37:44.220 I/yanzi   ( 4917): onSurfaceTextureUpdated...	Line 587: 06-22 12:37:44.253 I/yanzi   ( 4917): onSurfaceTextureUpdated...

3、Camera再执行startPreview时必须保证TextureView的SurfaceTexture上来了，如果因为一些性能原因onSurfaceTextureAvailable()这个回调上不来就开预览，就开不了的。如果发生这种情况，就在onSurfaceTextureAvailable()回调里执行open和startPreview操作，保证万无一失。

4、TextureView本身就有getSurfaceTexture()这个函数，我又封装了个:

	/* 让Activity能得到TextureView的SurfaceTexture	 * @see android.view.TextureView#getSurfaceTexture()	 */	public SurfaceTexture _getSurfaceTexture(){		return mSurface;	}

textureView.getSurfaceTexture(),把它传给Camera： mCamera.setPreviewTexture(surface);也是能正常预览的。但是推荐使用前者，原因见官方上的这段话:

A TextureView's SurfaceTexture can be obtained either by invoking getSurfaceTexture() or by using a TextureView.SurfaceTextureListener. It is important to know that a SurfaceTexture is available only after the TextureView is attached to a window (and onAttachedToWindow() has been invoked.) It is therefore highly recommended you use a listener to be notified when the SurfaceTexture becomes available.

两种方式获得SurfaceTexture，推荐使用监听。因为只有在TextureView执行完onAttachedToWindow时，它的tSurfaceTexture才上来。

5、SurfaceTexture和TextureView的关系:

Using a TextureView is simple: all you need to do is get its SurfaceTexture. The SurfaceTexture can then be used to render content

如果说TextureView是一幅画的话，那SurfaceTexture就是画布，真正渲染的载体是SurfaceTexture。

6、TextureView可以像一般View执行各种变化，其中有个textureView.setAlpha(1.0f);默认不写这句话，它的alpha也是1.0f,即不透明。如果设成透明0.0f，可以看到啥都看不到了，这一点跟Surfaceview刚好相反。Surfaceview的SurfaceHolder一般要设一下Transparent即透明。但TextureView因为是个view，任何一个png的照片透明度设成0肯定啥都看不到。

7、如果认为预览个Camera这就是TextureView和SurfaceTexture的使命的话，就大错特错了，真正用意是和OpenGL无缝连接。

--------------------本文系原创，转载请注明作者yanzi1225627

版本号:PlayCamera_V2.0.0[2014-6-22].zip

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