使用Glass GDK和Android Camera API时，消息“相机已停止”

Question

我想知道是否有人尝试使用标准Android Camera API（http://developer.android.com/guide/topics/media/camera.html）来控制应用中的相机。

我能够使用startActivityForResult（）方法让我的应用程序工作，但是对于从文件系统返回图像花了多长时间有点失望，所以我想尝试其他路径，使用CameraPreview。

我根据Android Camera API示例设置了一些代码，它构建并运行良好，但在 surfaceChanged 执行后，我在屏幕上收到一条消息“The相机已停止。“

稍后编辑 - 我将相机活动移动到自己的项目中，现在它可以工作，但它会让预览变得混乱。但在拍完照片后它显示得很好。这是布局代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
  <FrameLayout
    android:id="@+id/camera_preview"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="1"
    />
</LinearLayout>

这是活动来源：

package com.example.cameratest;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

import com.google.android.glass.touchpad.Gesture;
import com.google.android.glass.touchpad.GestureDetector;

import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore.Files.FileColumns;
import android.app.Activity;
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.util.Log;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.WindowManager;
import android.widget.FrameLayout;

public class MainActivity extends Activity {

private static final String TAG = MainActivity.class.getSimpleName();

private GestureDetector mGestureDetector;

private Camera mCamera;
private CameraPreview mPreview;

private static boolean gotCamera = false;

private PictureCallback mPicture = new PictureCallback() {
    @Override
    public void onPictureTaken(byte[] data, Camera camera) {
        File pictureFile = getOutputMediaFile(FileColumns.MEDIA_TYPE_IMAGE);
        if (pictureFile == null){
            Log.d(TAG, "Error creating media file, check storage permissions");
            return;
        }
        try {
            FileOutputStream fos = new FileOutputStream(pictureFile);
            fos.write(data);
            fos.close();
        } catch (FileNotFoundException e) {
            Log.d(TAG, "File not found: " + e.getMessage());
        } catch (IOException e) {
            Log.d(TAG, "Error accessing file: " + e.getMessage());
        }
    }
};

/** Create a file Uri for saving an image or video */
private static Uri getOutputMediaFileUri(int type){
    return Uri.fromFile(getOutputMediaFile(type));
}

/** Create a File for saving an image or video */
private static File getOutputMediaFile(int type){
    // To be safe, you should check that the SDCard is mounted
    // using Environment.getExternalStorageState() before doing this.

    File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
              Environment.DIRECTORY_PICTURES), "MyCameraApp");
    // This location works best if you want the created images to be shared
    // between applications and persist after your app has been uninstalled.

    // Create the storage directory if it does not exist
    if (! mediaStorageDir.exists()){
        if (! mediaStorageDir.mkdirs()){
            Log.d("MyCameraApp", "failed to create directory");
            return null;
        }
    }

    // Create a media file name
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    File mediaFile;
    if (type == FileColumns.MEDIA_TYPE_IMAGE){
        mediaFile = new File(mediaStorageDir.getPath() + File.separator +
                "IMG_"+ timeStamp + ".jpg");
    } else if(type == FileColumns.MEDIA_TYPE_VIDEO) {
        mediaFile = new File(mediaStorageDir.getPath() + File.separator +
                "VID_"+ timeStamp + ".mp4");
    } else {
        return null;
    }

    return mediaFile;
}

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

    getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

    mGestureDetector = createGestureDetector(this);

    setContentView(R.layout.activity_main);

    // Create an instance of Camera
    mCamera = getCameraInstance();

    if (gotCamera) {
        // Create our Preview view and set it as the content of our activity.
        Log.v(TAG,"We got the camera");
        mPreview = new CameraPreview(this, mCamera);
        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
        preview.addView(mPreview);
    }
    else {
        finish();
    }


}

private static Camera getCameraInstance(){
    gotCamera = false;
    Camera c = null;
    try {
        c = Camera.open(); // attempt to get a Camera instance
        gotCamera = true;
    }
    catch (Exception e){
        // Camera is not available (in use or does not exist)
        Log.v(TAG,"Camera is not available!");
    }
    return c; // returns null if camera is unavailable
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

/*
 * Send generic motion events to the gesture detector
 */
@Override
public boolean onGenericMotionEvent(MotionEvent event) {
    if (mGestureDetector != null) {
        return mGestureDetector.onMotionEvent(event);
    }
    return false;
}

private GestureDetector createGestureDetector(Context context) {
    GestureDetector gestureDetector = new GestureDetector(context);
        //Create a base listener for generic gestures
        gestureDetector.setBaseListener( new GestureDetector.BaseListener() {
            @Override
            public boolean onGesture(Gesture gesture) {
                if (gesture == Gesture.TAP) {
                    // do something on tap
                    Log.v(TAG,"tap");

                    // take a picture
                    takePic();

                    return true;
                } else if (gesture == Gesture.TWO_TAP) {
                    // do something on two finger tap
                    return true;
                } else if (gesture == Gesture.SWIPE_RIGHT) {
                    // do something on right (forward) swipe
                    return true;
                } else if (gesture == Gesture.SWIPE_LEFT) {
                    // do something on left (backwards) swipe
                    return true;
                }
                return false;
            }
        });
        gestureDetector.setFingerListener(new GestureDetector.FingerListener() {
            @Override
            public void onFingerCountChanged(int previousCount, int currentCount) {
              // do something on finger count changes
            }
        });
        gestureDetector.setScrollListener(new GestureDetector.ScrollListener() {
            @Override
            public boolean onScroll(float displacement, float delta, float velocity) {
                // do something on scrolling
                return false;
            }
        });
        return gestureDetector;
    }

private class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    private Camera mCamera;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;

        Log.v(TAG,"In CameraPreview");

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

        Log.v(TAG,"Got holder");

        mHolder.addCallback(this);

        Log.v(TAG,"Added callback");

        // 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 {
            Log.v(TAG,"in surface created");
            mCamera.setPreviewDisplay(holder);
            Log.v(TAG,"set preview display");
            mCamera.startPreview();
            Log.v(TAG,"preview started");
        } 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.
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    }

    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.v(TAG,"in surface changted");

        if (mHolder.getSurface() == null){
          // preview surface does not exist
            Log.v(TAG,"surface don't exist");
          return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
            Log.v(TAG,"stopped preview");
        } catch (Exception e){
          // ignore: tried to stop a non-existent preview
            Log.v(TAG,"preview e");
        }

        // start preview with new settings
        try {
            Log.v(TAG,"startpreview");
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();

        } catch (Exception e){
            Log.d(TAG, "Error starting camera preview: " + e.getMessage());
        }
    }
}

public void takePic() {
    // get an image from the camera
    mCamera.takePicture(null, null, mPicture);
}

}

Answer 1

你为surfaceChanged所拥有的代码看起来很好，类似于我在Glass工作中使用的代码。您是否检查过传递给Camera.setParameters的相机参数，例如预览尺寸和对焦模式？如果您可以在有助于发现问题的问题中发布完整的活动来源。