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。
事实上关于怎样用TextureView预览Camera，官网已经给出了demo，參见这里。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框架来高速替换掉Surfaceview。由于用Surfaceview预览的话传一个SurfaceHolder进去，用Textureview预览的话须要传进去一个SurfaceTexture。其它的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，最基本的目的是在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;
}
}
二、在布局文件中把它加上即可了，由于他的父类就是View。当成一般的View即可<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>
三、在CameraInterface里，我封装了两个函数:
/**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);
}
}分别相应Surfaceview和TextureView预览。能够看到就是传进来的參数不一样，initCamera()的东西都一样。 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(); //又一次get一次
Log.i(TAG, "终于设置:PreviewSize--With = " + mParams.getPreviewSize().width
+ "Height = " + mParams.getPreviewSize().height);
Log.i(TAG, "终于设置:PictureSize--With = " + mParams.getPictureSize().width
+ "Height = " + mParams.getPictureSize().height);
}
}四、在Activity里，依然开一个线程去open Camera:
Thread openThread = new Thread(){
@Override
public void run() {
// TODO Auto-generated method stub
CameraInterface.getInstance().doOpenCamera(CameraActivity.this);
}
};
openThread.start();在Camera Open完的回调里开预览:
@Override
public void cameraHasOpened() {
// TODO Auto-generated method stub
SurfaceTexture surface = textureView._getSurfaceTexture();
CameraInterface.getInstance().doStartPreview(surface, previewRate);
}之后就能正常运行了。能够看到与前文Surfaceview预览Camera 修改非常之小。
几个注意事项:
1、TextureView是Android 4.0之后增加的，低版本号么这个类。TextureView必须工作在开启硬件加速的环境中。也即配置文件中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。但假设写成false，能够看到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): 终于设置:PreviewSize--With = 800Height = 448
Line 557: 06-22 12:37:43.874 I/yanzi ( 4917): 终于设置: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...測试手机为中兴Geek。这个手机Camera还是非常牛逼的，比手里的华为G700强。就是偶尔会连不上Camera Service，汗。
从log能够看到。onSurfaceTextureAvailable这个回调须要一定时间。Camera.open()这句话用了130多ms。但有两点跟Surfaceview不同。第一，TextureView创建过程中没有进到onSurfaceTextureSizeChanged()这个函数里。而SurfaceView在创建过程中，从无到有的时候会进到大小发生变化回调里。
第二。onSurfaceTextureUpdated()这个函数每上来一帧数据，这块就进来一次。
这是跟Surfaceview相比。最伟大的一个地方。
通过这个接口。能够将上来的SurfaceTexture送给OpenGL再去处理。
这个回调是实时的。而非用Camera的PreviewCallback这样的2次回调的方式。
从时间看，基本上每32ms左右上来一帧数据，即每秒30帧。跟本手机的Camera的性能吻合。
3、Camera再运行startPreview时必须保证TextureView的SurfaceTexture上来了，假设由于一些性能原因onSurfaceTextureAvailable()这个回调上不来就开预览，就开不了的。假设发生这样的情况，就在onSurfaceTextureAvailable()回调里运行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;
}这里的mSurface就是onSurfaceTextureAvailable()回调里传上来的SurfaceTexture。測试证明。开预览时直接调textureView.getSurfaceTexture(),把它传给Camera： mCamera.setPreviewTexture(surface);也是能正常预览的。
可是推荐使用前者，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。由于仅仅有在TextureView运行完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
假设说TextureView是一幅画的话，那SurfaceTexture就是画布，真正渲染的载体是SurfaceTexture。
6、TextureView能够像一般View运行各种变化。当中有个textureView.setAlpha(1.0f);默认不写这句话，它的alpha也是1.0f,即不透明。
假设设成透明0.0f，能够看到啥都看不到了，这一点跟Surfaceview刚好相反。
Surfaceview的SurfaceHolder一般要设一下Transparent即透明。但TextureView由于是个view，不论什么一个png的照片透明度设成0肯定啥都看不到。
7、假设觉得预览个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
版本号号:PlayCamera_V2.0.0[2014-6-22].zip
CSDN下载链接:http://download.csdn.net/detail/yanzi1225627/7540903
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