java - 菜单 Intent 上的相机预览卡住

Question

我有一个 Glass 应用程序，我在其中尝试使用 Live Card 从菜单选项启动相机预览 Activity 。当我离开 Live Card(比如天气)并返回时，应用程序似乎卡住了，然后尝试通过菜单选项调出相机。抱歉所有代码，这里有以下文件:

服务.java

. . .
   @Override
    public IBinder onBind(Intent intent) { return mBinder; }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        if (mLiveCard == null) {
            mLiveCard = new LiveCard(this, LIVE_CARD_TAG);

            mRemoteViews = new RemoteViews(getPackageName(), R.layout.service_layout);
            mLiveCard.setViews(mRemoteViews);

            // Display the options menu when the live card is tapped.
            Intent menuIntent = new Intent(this, MenuActivity.class);
            menuIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK |
                    Intent.FLAG_ACTIVITY_CLEAR_TASK);

            mLiveCard.setAction(PendingIntent.getActivity(this, 0, menuIntent, 0));
            mLiveCard.attach(this);
            mLiveCard.publish(PublishMode.REVEAL);

        } else {
            mLiveCard.navigate();
        }
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        if (mLiveCard != null && mLiveCard.isPublished()) {
            mLiveCard.unpublish();
            mLiveCard = null;
        }
        super.onDestroy();
    }
}

MenuActivity.java

public class MenuActivity extends Activity {

    @Override
    public void onAttachedToWindow() {
        super.onAttachedToWindow();
        // Open the options menu right away.
        openOptionsMenu();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.layout, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        switch (item.getItemId()) {
            case R.id.action_stop:
                // Stop the service which will unpublish the live card.
                stopService(new Intent(MenuActivity.this, Service.class));
                return true;

            case R.id.action_camera:
                startActivity(new Intent(MenuActivity.this, Camera.class));
                return true;

            default:
                return super.onOptionsItemSelected(item);
        }
    }

    @Override
    public void onOptionsMenuClosed(Menu menu) { finish(); }
}

相机.java

public class Camera extends Activity {

    private SurfaceView mPreview = null;
    private SurfaceHolder mPreviewHolder = null;
    private Camera mCamera = null;
    private boolean inPreview = false;
    private boolean cameraConfigured = false;

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.camera);


        mPreview = (SurfaceView) findViewById(R.id.camera_preview);
        mPreviewHolder = mPreview.getHolder();
        mPreviewHolder.addCallback(surfaceCallback);
    }


    @Override
    public void onResume() {
        super.onResume();

        mCamera = Camera.open();
        startPreview();
    }

    @Override
    public void onPause() {
        super.onPause();

        if (inPreview) {
            mCamera.stopPreview();
        }

        mCamera.release();
        mCamera = null;
        inPreview = false;
    }

    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);
    }

    private void initPreview(int width, int height) {
        if (mCamera != null && mPreviewHolder.getSurface() != null) {
            try {
                mCamera.setPreviewDisplay(mPreviewHolder);
            } catch (Throwable t) {
                Log.e("PreviewDemo-surfaceCallback",
                        "Exception in setPreviewDisplay()", t);
            }

            if (!cameraConfigured) {
                Camera.Parameters parameters = mCamera.getParameters();
                Camera.Size size = getBestPreviewSize(width, height,
                        parameters);

                if (size != null) {
                    parameters.setPreviewSize(size.width, size.height);
                    mCamera.setParameters(parameters);
                    cameraConfigured = true;
                }
            }
        }
    }

    private void startPreview() {
        if (cameraConfigured && mCamera != null) {
            mCamera.startPreview();
            inPreview = true;
        }
    }

我似乎无法弄清楚为什么相机预览最初有效但在导航离开时不起作用。我觉得这里缺少一些简单的东西。任何帮助将不胜感激!

Answer 1

我不确定这是否能解决您的问题，但我会以这种方式启动和停止相机:

private Camera getCameraInstance() {
    Camera mCamera = null;
    try {
        /* attempt to get a Camera instance */
        mCamera = Camera.open();
    } catch (Exception e) {
        /* Camera is not available (in use or does not exist) */
        Log.e(TAG, "Error getting camera: " + e.getMessage());
        // process null error here
        // finish();
    }

    /* returns null if camera is unavailable */
    return mCamera;
}


@Override
public void onResume() {
    super.onResume();

    if (mCamera == null) {

        mCamera = getCameraInstance();

        if (mCamera != null) {
            startPreview();
        } else {
            // process null error here
        }
    }
}

@Override
public void onPause() {
    super.onPause();

    if (mCamera != null) {
        /* stop preview */
        if (inPreview) {
            try {
                mCamera.stopPreview();
            } catch (Exception e) {
                /* ignore: tried to stop a non-existent preview */
            }
        }

        /* release the camera */
        mCamera.release();
        mCamera = null;
        inPreview = false;
    }
} 

我还会在 initPreview 中检查 mCamera 或 getSurface 是否为 null。

private void initPreview(int width, int height) {
    if (mCamera != null && mPreviewHolder.getSurface() != null) {
        try {
            mCamera.setPreviewDisplay(mPreviewHolder);
        } catch (Throwable t) {
            Log.e("PreviewDemo-surfaceCallback",
                    "Exception in setPreviewDisplay()", t);
        }

        if (!cameraConfigured) {
            Camera.Parameters parameters = mCamera.getParameters();
            Camera.Size size = getBestPreviewSize(width, height,
                    parameters);

            if (size != null) {
                parameters.setPreviewSize(size.width, size.height);
                mCamera.setParameters(parameters);
                cameraConfigured = true;
            }
        }
    } else {
        Log.e(TAG, "Camera or getSurface is null");
    }
}