android camera preview | 易学教程

问题

I have a problem. I'm trying to develop a program that uses the camera, everything is working in my device but like many of you know the CameraPreview doesn't work the same way in all devices, so I tried to integrate the code that google provides in this address:

http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/graphics/CameraPreview.html

The problem I've faced is that I don't know how to integrate to my project, here is my code and what I've done without exceeding:

Preview mPreview;
private Camera mCamera;

    @Override
public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mPreview = new Preview(this);

        //ContentView----------------------------------------------------------
        setContentView(R.layout.main);

        mSurfaceView = (SurfaceView)findViewById(R.id.camera_surface);

        mPreview.surfacemetod(mSurfaceView);

   @Override
   protected void onResume() {
      // TODO Auto-generated method stub
      super.onResume();    

      mCamera = Camera.open();
      mPreview.setCamera(mCamera);

Then the Preview class:

class Preview extends ViewGroup implements SurfaceHolder.Callback {
private final String TAG = "Preview";

SurfaceView mSurfaceView;
SurfaceHolder mHolder;
Size mPreviewSize;
List<Size> mSupportedPreviewSizes;
Camera mCamera;

Preview(Context context) {
    super(context);

    mSurfaceView = new SurfaceView(context);
    addView(mSurfaceView);

}

public void surfacemetod(SurfaceView surface){

    //mSurfaceView = new SurfaceView(context);
    //addView(mSurfaceView);

    // Install a SurfaceHolder.Callback so we get notified when the
    // underlying surface is created and destroyed.
    mHolder = mSurfaceView.getHolder();
    mHolder.addCallback(this);
    mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

}

public void setCamera(Camera camera) {
    mCamera = camera;
    if (mCamera != null) {
        mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();
        requestLayout();
    }
}

After this code there are all the methods in the link above that I didn't copy to save space.

The question is that when I run the code the mPreviewSize.with and mPreviewSize.height

public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
    // Now that the size is known, set up the camera parameters and begin
    // the preview.
    Camera.Parameters parameters = mCamera.getParameters();
    parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
    requestLayout();

    mCamera.setParameters(parameters);
    mCamera.startPreview();
}

are null and I get a FORCE CLOSE

Essentially looks like it doesn't get inside OnMeasure to resolve them. Any idea?

This is the log:

02-16 13:54:26.068: ERROR/AndroidRuntime(24374): FATAL EXCEPTION: main

02-16 13:54:26.068: ERROR/AndroidRuntime(24374): java.lang.NullPointerException

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at com.dashboard.camera.lite.Preview.surfaceChanged(Preview.java:162)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.SurfaceView.updateWindow(SurfaceView.java:554)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.SurfaceView.dispatchDraw(SurfaceView.java:341)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.ViewGroup.drawChild(ViewGroup.java:1638)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.ViewGroup.drawChild(ViewGroup.java:1638)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.View.draw(View.java:6796)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.widget.FrameLayout.draw(FrameLayout.java:354)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.ViewGroup.drawChild(ViewGroup.java:1640)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.View.draw(View.java:6796)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.widget.FrameLayout.draw(FrameLayout.java:354)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1894)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.ViewRoot.draw(ViewRoot.java:1432)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1174)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1752)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.os.Handler.dispatchMessage(Handler.java:99)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.os.Looper.loop(Looper.java:123)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at android.app.ActivityThread.main(ActivityThread.java:4627)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at java.lang.reflect.Method.invokeNative(Native Method)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at java.lang.reflect.Method.invoke(Method.java:521)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

02-16 13:54:26.068: ERROR/AndroidRuntime(24374):     at dalvik.system.NativeStart.main(Native Method)

回答1:

can you pass the log? I predict that you have a problem with mPreview.width/height - it is propably some incorrect value.

来源：https://stackoverflow.com/questions/5015635/android-camera-preview

标签

android

camera

preview