camera.setParameters 在 android 中失败

Question

我在我的应用程序中包含了相机功能。我还在市场上推出了该应用程序。我从其中一位用户那里收到一条错误消息，说他在打开相机时遇到了错误。

我已经在 2.1 的设备上测试了该应用程序。我从用户那里得到的错误是使用nexus one，它主要运行2.2...这是我收到的logcat错误...

java.lang.RuntimeException: setParameters failed
at android.hardware.Camera.native_setParameters(Native Method)
at android.hardware.Camera.setParameters(Camera.java:647)
at com.CameraApp.Preview.surfaceChanged(Preview.java:67)
at android.view.SurfaceView.updateWindow(SurfaceView.java:538)
at android.view.SurfaceView.dispatchDraw(SurfaceView.java:339)
at android.view.ViewGroup.drawChild(ViewGroup.java:1638)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
at android.view.ViewGroup.drawChild(ViewGroup.java:1638)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
at android.view.ViewGroup.drawChild(ViewGroup.java:1638)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
at android.view.View.draw(View.java:6743)
at android.widget.FrameLayout.draw(FrameLayout.java:352)
at android.view.ViewGroup.drawChild(ViewGroup.java:1640)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
at android.view.View.draw(View.java:6743)
at android.widget.FrameLayout.draw(FrameLayout.java:352)
at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1842)
at android.view.ViewRoot.draw(ViewRoot.java:1407)
at android.view.ViewRoot.performTraversals(ViewRoot.java:1163)
at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4627)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
at dalvik.system.NativeStart.main(Native Method)

我也在 2.2 模拟器上运行了该应用程序来检查它。但它工作得很好。谁能告诉我为什么会发生错误？

这是我在 cmets 中提到的类：

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

    SurfaceHolder mHolder;
    public Camera camera;

    Preview(Context context) 
    {
        super(context);

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

    public void surfaceCreated(SurfaceHolder holder) 
    {
        // The Surface has been created, acquire the camera and tell it where
        // to draw.
         camera = Camera.open();
        try {
        camera.setPreviewDisplay(holder);
        } catch (IOException exception) {
        camera.release();
        camera = null;
            // TODO: add more exception handling logic here
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) 
    {
        // Surface will be destroyed when we return, so stop the preview.
        // Because the CameraDevice object is not a shared resource, it's very
        // important to release it when the activity is paused.
        camera.stopPreview();
        camera.release();
        camera = null;
    }

    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 = camera.getParameters();
        parameters.setPreviewSize(w, h);
        camera.setParameters(parameters);
        camera.startPreview();
    }

    @Override
    public void draw(Canvas canvas) 
    {
        super.draw(canvas);
        Paint p= new Paint(Color.RED);
        Log.d(TAG,"draw");
        canvas.drawText("PREVIEW", canvas.getWidth()/2, canvas.getHeight()/2, p );
    }
}

Answer 1

失败是因为并非所有设备都支持任意预览尺寸。显然有些人这样做，但你不能依赖它。在您的 surfaceChanged 方法中，您需要执行以下操作：

public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
    Camera.Parameters parameters = camera.getParameters();
    List<Camera.Size> previewSizes = parameters.getSupportedPreviewSizes();

    // You need to choose the most appropriate previewSize for your app
    Camera.Size previewSize = // .... select one of previewSizes here

    parameters.setPreviewSize(previewSize.width, previewSize.height);
    camera.setParameters(parameters);
    camera.startPreview();
}

您必须想办法对其进行缩放，以免丢失纵横比等。

这里的参考是Android SDK doc。