我使用下面的代码来显示surfaceView中的front_camera，但是当我在三星Galaxy S plus上尝试此代码时，所有屏幕均为黑色，但未出现错误。有谁知道它为什么会发生？Android - 前置摄像头预览SurfaceView
public class TestLedActivity extends Activity {
private SurfaceView preview=null;
private SurfaceHolder previewHolder=null;
private Camera camera=null;
private boolean inPreview=false;
private int id;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
int currentapiVersion = android.os.Build.VERSION.SDK_INT;
if (currentapiVersion > android.os.Build.VERSION_CODES.FROYO){
id=findFrontFacingCamera();
Log.d("TestLedActivity","L'id trovato e': "+id);
camera = Camera.open(id);
} else{
Log.d("TestLedActivity","La versione e' froyo");
camera = Camera.open();
}
preview=(SurfaceView)findViewById(R.id.cpPreview);
// TODO Auto-generated method stub
previewHolder=preview.getHolder();
previewHolder.addCallback(surfaceCallback);
previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
@Override
public void onResume() {
super.onResume();
}
@Override
public void onPause() {
if (inPreview) {
camera.stopPreview();
}
camera.release();
camera=null;
inPreview=false;
super.onPause();
}
private int findFrontFacingCamera() {
int idCamera=0;
// Look for front-facing camera, using the Gingerbread API.
// Java reflection is used for backwards compatibility with pre-Gingerbread APIs.
try {
Class> cameraClass = Class.forName("android.hardware.Camera");
Object cameraInfo = null;
Field field = null;
int cameraCount = 0;
Method getNumberOfCamerasMethod = cameraClass.getMethod("getNumberOfCameras");
if (getNumberOfCamerasMethod != null) {
cameraCount = (Integer) getNumberOfCamerasMethod.invoke(null, (Object[]) null);
}
Class> cameraInfoClass = Class.forName("android.hardware.Camera$CameraInfo");
if (cameraInfoClass != null) {
cameraInfo = cameraInfoClass.newInstance();
}
if (cameraInfo != null) {
field = cameraInfo.getClass().getField("facing");
}
Method getCameraInfoMethod = cameraClass.getMethod("getCameraInfo", Integer.TYPE, cameraInfoClass);
if (getCameraInfoMethod != null && cameraInfoClass != null && field != null) {
for (int camIdx = 0; camIdx < cameraCount; camIdx++) {
getCameraInfoMethod.invoke(null, camIdx, cameraInfo);
int facing = field.getInt(cameraInfo);
if (facing == 1) { // Camera.CameraInfo.CAMERA_FACING_FRONT
try {
Method cameraOpenMethod = cameraClass.getMethod("open", Integer.TYPE);
if (cameraOpenMethod != null) {
Log.d("TestLedActivity","Id frontale trovato: "+camIdx);
//camera = (Camera) cameraOpenMethod.invoke(null, camIdx);
idCamera=camIdx;
}
} catch (RuntimeException e) {
Log.e("TestLedActivity", "Camera failed to open: " + e.getLocalizedMessage());
}
}
}
}
}
// Ignore the bevy of checked exceptions the Java Reflection API throws - if it fails, who cares.
catch (ClassNotFoundException e ) {Log.e("TestLedActivity", "ClassNotFoundException" + e.getLocalizedMessage());}
catch (NoSuchMethodException e ) {Log.e("TestLedActivity", "NoSuchMethodException" + e.getLocalizedMessage());}
catch (NoSuchFieldException e ) {Log.e("TestLedActivity", "NoSuchFieldException" + e.getLocalizedMessage());}
catch (IllegalAccessException e ) {Log.e("TestLedActivity", "IllegalAccessException" + e.getLocalizedMessage());}
catch (InvocationTargetException e ) {Log.e("TestLedActivity", "InvocationTargetException" + e.getLocalizedMessage());}
catch (InstantiationException e ) {Log.e("TestLedActivity", "InstantiationException" + e.getLocalizedMessage());}
catch (SecurityException e ) {Log.e("TestLedActivity", "SecurityException" + e.getLocalizedMessage());}
if (camera == null) {
Log.d("TestLedActivity","Devo aprire la camera dietro");
// Try using the pre-Gingerbread APIs to open the camera.
idCamera=0;
}
return idCamera;
}
private Camera.Size getBestPreviewSize(int width, int height,
Camera.Parameters parameters) {
Camera.Size result=null;
for (Camera.Size size : parameters.getSupportedPreviewSizes()) {
if (size.width<=width && size.height<=height) {
if (result==null) {
result=size;
}
else {
int resultArea=result.width*result.height;
int newArea=size.width*size.height;
if (newArea>resultArea) {
result=size;
}
}
}
}
return(result);
}
SurfaceHolder.Callback surfaceCallback=new SurfaceHolder.Callback() {
public void surfaceCreated(SurfaceHolder holder) {
try {
camera.setPreviewDisplay(previewHolder);
}
catch (Throwable t) {
Log.e("PreviewDemo-surfaceCallback",
"Exception in setPreviewDisplay()", t);
Toast
.makeText(TestLedActivity.this, t.getMessage(), Toast.LENGTH_LONG)
.show();
}
}
@Override
public void surfaceChanged(SurfaceHolder holder,
int format, int width,
int height) {
Camera.Parameters parameters=camera.getParameters();
Camera.Size size=getBestPreviewSize(width, height,
parameters);
if (size!=null) {
//parameters.set("camera-id", 0);
parameters.setPreviewSize(size.width, size.height);
camera.setParameters(parameters);
camera.startPreview();
inPreview=true;
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// no-op
}
};
}
