我正在创建一个相机应用程序，但我在startPreview上遇到了问题，它向我发送：
java.lang.RuntimeException: startPreview failed
这是我的相机活动：
public class CameraActivity extends Activity {
private Camera mCamera;
private CameraPreview mPreview;
private Target_Frame targetFrame;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.camera_layout);
mCamera=getCameraInstance();
mPreview=new CameraPreview(this, mCamera);
FrameLayout preview=(FrameLayout)findViewById(R.id.camera_preview);
preview.addView(mPreview);
}
/** Check if this device has a camera only if not specified in the manifest */
public boolean checkCameraHardware(Context context) {
if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
// this device has a camera
return true;
} else {
// no camera on this device
return false;
}
}
/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
Camera c = null;
try {
c = Camera.open(); // attempt to get a Camera instance
}
catch (Exception e){
// Camera is not available (in use or does not exist)
}
return c; // returns null if camera is unavailable
}
/**Check if the device has flash*/
public boolean checkFlash(Context context){
if(context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH)){
//the device has flash
return true;
}else{
//no flash
return false;
}
}
@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
releaseCamera();
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
releaseCamera();
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
//Test if i have to put all this code like in onCreate
if(mCamera!=null){
return;
}
mCamera=getCameraInstance();
if(mPreview!=null){
return;
}
mPreview=new CameraPreview(this, mCamera);
FrameLayout preview=(FrameLayout)findViewById(R.id.camera_preview);
preview.addView(mPreview);
}
private void releaseCamera(){
if (mCamera != null){
mCamera.release(); // release the camera for other applications
mCamera = null;
}
}}
这是我的SurfaceView代码：
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private static final String TAG = "CameraPreview";
private SurfaceHolder mHolder;
private Camera mCamera;
public CameraPreview(Context context, Camera camera) {
super(context);
mCamera = camera;
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
// deprecated setting, but required on Android versions prior to 3.0
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, now tell the camera where to draw the preview.
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// empty. Take care of releasing the Camera preview in your activity.
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
if (mHolder.getSurface() == null){
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize, rotate or
// reformatting changes here
Parameters parameters= mCamera.getParameters();
parameters.setPreviewSize(w, h);
mCamera.setParameters(parameters);
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e){
Log.d(TAG, "Error starting camera preview: " + e.getMessage());
}
}
}
这是我的错误日志：
12-01 13:17:01.135: E/AndroidRuntime(1161): FATAL EXCEPTION: main
12-01 13:17:01.135: E/AndroidRuntime(1161): java.lang.RuntimeException: startPreview
12-01 13:17:01.135: E/AndroidRuntime(1161): at com.example.prueba.CameraPreview.surfaceCreated(CameraPreview.java:36)
我已经解决了删除表面中的一些行的问题已更改
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
Log.d("Function", "surfaceChanged iniciado");
if (mHolder.getSurface() == null){
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize, rotate or
// reformatting changes here
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e){
Log.d(TAG, "Error starting camera preview: " + e.getMessage());
}
}
所以错误必须在以下行之一中：
Parameters parameters= mCamera.getParameters();
parameters.setPreviewSize(w, h);
mCamera.setParameters(parameters);
有人可以解释我这些台词有什么问题吗？
（w， h） 是相机的有效预览尺寸吗？
您可以使用mCamera.getParameters().getSupportedPreviewSizes()获取所有有效的预览大小。
晚了，但如果有人在寻找答案
变量 w 和 h 不是最佳预览大小。您可以使用该功能获得最佳预览大小
public static Camera.Size getOptimalPreviewSize(List<Camera.Size> sizes, int w, int h) {
final double ASPECT_TOLERANCE = 0.1;
double targetRatio=(double)h / w;
if (sizes == null) return null;
Camera.Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
for (Camera.Size size : sizes) {
double ratio = (double) size.width / size.height;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
if (optimalSize == null) {
minDiff = Double.MAX_VALUE;
for (Camera.Size size : sizes) {
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
您可以使用
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
..
size=getOptimalPreviewSize(parameters.getSupportedPreviewSizes(), w, h);
parameters.setPreviewSize(size.getWidth(), size.getHeight());
..
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, now tell the camera where to draw the preview.
try {
mCamera.setPreviewDisplay(holder);
mCamera.getParameters().getSupportedPreviewSizes();
mCamera.startPreview();
Log.d(TAG, "Camera preview started.");
} catch (IOException e) {
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
}
}
我遇到了这个错误，这是因为我第一次启动应用程序时没有在暂停时调用 releaseCamera。
重新启动后，一切正常^^