Question

我已经尝试了一切，但我仍然无法解决这个问题。

我正在应用中实现相机功能，除自动对焦外，一切正常。当我调用autoFocus（）时，它会抛出异常，我无法理解为什么。我在Desire HD上运行代码。

代码：

@Override
protected void onStart() {
     super.onStart();

     //grab seurface view and callback
     cameraView = (CameraSurfaceView) findViewById(R.id.cameraView);
     try{
        camera = Camera.open();
        cameraView.setCamera(camera);
        //release previous autofocus and assign new one
        camera.cancelAutoFocus();
        camera.autoFocus(new Camera.AutoFocusCallback() {

                public void onAutoFocus(boolean success, Camera camera) {
                // TODO Auto-generated method stub

                }});
    }
    catch (Exception e) {
        //had an issue accessing the camera prompt user
        //TODO create user prompt
        e.printStackTrace();
    }
}

堆栈追踪：

01-11 16:09:38.456: W/System.err(26546): java.lang.RuntimeException: autoFocus failed
01-11 16:09:38.456: W/System.err(26546):    at android.hardware.Camera.native_autoFocus(Native Method)
01-11 16:09:38.456: W/System.err(26546):    at android.hardware.Camera.autoFocus(Camera.java:680)
01-11 16:09:38.456: W/System.err(26546):    at com.myapp.MyActivity.onStart(BarcodeScannerActivity.java:57)
01-11 16:09:38.466: W/System.err(26546):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1201)
01-11 16:09:38.466: W/System.err(26546):    at android.app.Activity.performStart(Activity.java:3955)
01-11 16:09:38.466: W/System.err(26546):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1845)
01-11 16:09:38.466: W/System.err(26546):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1893)
01-11 16:09:38.466: W/System.err(26546):    at android.app.ActivityThread.access$1500(ActivityThread.java:135)
01-11 16:09:38.466: W/System.err(26546):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1054)
01-11 16:09:38.466: W/System.err(26546):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-11 16:09:38.466: W/System.err(26546):    at android.os.Looper.loop(Looper.java:150)
01-11 16:09:38.476: W/System.err(26546):    at android.app.ActivityThread.main(ActivityThread.java:4385)
01-11 16:09:38.476: W/System.err(26546):    at java.lang.reflect.Method.invokeNative(Native Method)
01-11 16:09:38.476: W/System.err(26546):    at java.lang.reflect.Method.invoke(Method.java:507)
01-11 16:09:38.476: W/System.err(26546):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
01-11 16:09:38.476: W/System.err(26546):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
01-11 16:09:38.476: W/System.err(26546):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

使用SurfaceHolder.Callback - ＆gt; surfaceCreated以了解何时可以启动AutoFocus。如果未创建曲面（持续一段时间），则自动对焦将失败。

Answer 2

您可能需要确保手机支持自动对焦。检查这个很容易：

Camera.Parameters p = mCamera.getParameters();
List<String> focusModes = p.getSupportedFocusModes();

if(focusModes != null && focusModes.contains(Camera.Parameters.FOCUS_MODE_AUTO)) {
    //Phone supports autofocus!
}
else {
    //Phone does not support autofocus!
}

Answer 3

我提出了两个对我有用的解决方案。 1）正确停止并恢复相机。我是通过在onPause和onResume上调用这些方法来实现的，也是在相机预览中间，我在我的应用程序中扫描QR码：

public void stopCamera(){
     mCamera.cancelAutoFocus();
     mCamera.setPreviewCallback(null);
     mCamera.stopPreview();  
     mPreviewing = false;
     }

public void rethrottleCamera(){
        updateViews(); //Updates my Layouts
        mPreviewing = true;
        mCamera.startPreview();
        mCamera.setPreviewCallback(previewCb);  
        mCamera.autoFocus(autoFocusCB); 
        }

2）非常棘手，但像魔术一样工作！确保在创建预览曲面后调用自动对焦。要执行此操作，请以200毫秒的延迟运行自动对焦，以便为要创建的曲面购买时间。通过在“CameraPreview”对象声明上按ctrl + clic来设置此项，例如：

CameraPreview my_camera;

查找“public void surfaceChanged”方法并进行此更改：

//Add a delay to AUTOFOCUS after mCamera.startpreview();!!:
    mCamera.startPreview();                 
    final Handler handler = new Handler();
    handler.postDelayed(new Runnable() {
        @Override
        public void run() {                    
            mCamera.autoFocus(autoFocusCallback);
            }
    }, 200); //<-200 millisecond delay

    //If you call autofocus right after startPreview, chances are,
    //that the previewSurface will have not been created yet,
    //and autofocus will fail:
    mCamera.startPreview();               //Bad idea!
    mCamera.autoFocus(autoFocusCallback); //Bad idea!

还有很多其他修复方法，但这两种方法可以节省您的一天。

Answer 4

我找到了一个很好的解决方案因此，让我们简单地捕获异常，并再次尝试在某些设备上调用自动对焦（即索尼体验和其他一些设备）什么是关于重试之间的延迟时间（1秒）
我不喜欢代码中的任何“魔术”数字，因此在某些情况下这可能太大或太小。它对我来说足够了）

public void requestAutoFocus(Handler handler, int message) {
    if(camera != null && previewing) {
        autoFocusCallback.setHandler(handler, message);
        scheduleAutoFocus();
    }
}

public void safeAutoFocus() {
    try {
        camera.autoFocus(autoFocusCallback);
    } catch (RuntimeException e) {
        // Horrible hack to deal with autofocus errors on Sony devices
        // See https://github.com/dm77/barcodescanner/issues/7 for example
        scheduleAutoFocus(); // wait 1 sec and then do check again
    }
}

private void scheduleAutoFocus() {
    mAutoFocusHandler.postDelayed(doAutoFocus, 1000);
}

private Runnable doAutoFocus = new Runnable() {
    public void run() {
        if(camera != null && previewing) {
            safeAutoFocus();
        }
    }
};

这里是启动和停止方法

public void startPreview() {
    if (camera != null && !previewing) {
        camera.startPreview();
        camera.autoFocus(autoFocusCallback);
        previewing = true;
    }
}

public void stopPreview() {
    if(camera != null && previewing) {
        try {
            camera.cancelAutoFocus();
            if(!useOneShotPreviewCallback) {
                camera.setPreviewCallback(null);
            }
            camera.stopPreview();
            previewCallback.setHandler(null, 0);
            autoFocusCallback.setHandler(null, 0);
            previewing = false;
        } catch(Exception e) {
            Log.e(TAG, e.toString(), e);
        }
    }
}

参考：https://github.com/dm77/barcodescanner/blob/master/core/src/main/java/me/dm7/barcodescanner/core/CameraPreview.java

Answer 5

确保在调用开始预览后调用autoFocus函数。根据{{3}}

此方法仅在预览处于活动状态时有效 startPreview（）和stopPreview（）之前。

如果您仍然遇到任何错误，请按同一顺序尝试android documentation和Rasmus's 解决方案。

Answer 6

有许多解决方案，但这是一个简单，便宜的选项，对我有用：

try{
   mCamera.autoFocus(autoFocusCB); //Or whatever part of code that crashes
   }
catch(Exception e){
   Log.v("joshtag","THIS PHONE DOES NOT SUPPORT AUTOFOCUS!!"); //a warning, popup, whatever
   }

瞧！陷阱已停用。

autoFocus抛出异常

6 个答案: