我的简单相机应用程序（android）在第一次尝试后不会加载相机视图
Posted
技术标签:
【中文标题】我的简单相机应用程序（android）在第一次尝试后不会加载相机视图【英文标题】：My simple camera app (android) won't load the camera view after the first attempt 【发布时间】：2017-03-24 09:18:30 【问题描述】：我只是想制作一个使用运行时权限的简单相机应用程序......它似乎在第一次启动应用程序时加载良好（请求相机权限）。允许访问后，它可以工作......但是一旦我关闭它并重新启动它，它只会显示一个白色图像，我的图标不会响应。我已经在应用程序中手动检查了权限，并且相机仍然被授予访问权限，但我认为我搞砸了我的权限代码。
这是 MainActivity 代码：
public class MainActivity extends AppCompatActivity
private static final int MY_PERMISSIONS_REQUEST_CAMERA = 1;
private Camera mCamera = null;
private Camera mCameraFront = null;
private CameraView mCameraView = null;
public int switchCamera = 1;
// int permissionCheck = ContextCompat.checkSelfPermission(this,
// Manifest.permission.CAMERA);
// String[] perms = "android.permission.CAMERA";
// int permsRequestCode = 200;
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.CAMERA)
!= PackageManager.PERMISSION_GRANTED)
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.CAMERA))
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
else
// No explanation needed, we can request the permission.
ActivityCompat.requestPermissions(this,
new String[]Manifest.permission.CAMERA,
MY_PERMISSIONS_REQUEST_CAMERA);
try
mCamera = Camera.open(1);//you can use open(int) to use different cameras
catch (Exception e)
Log.d("ERROR", "Failed to get camera: " + e.getMessage());
SwapCamera();
// if (mCamera != null)
//// mCameraView = new CameraView(this, mCamera);//create a SurfaceView to show camera data
//// FrameLayout camera_view = (FrameLayout)findViewById(R.id.camera_view);
//// camera_view.addView(mCameraView);//add the SurfaceView to the layout
// SwapCamera();
//
//btn to close the application
ImageButton imgClose = (ImageButton) findViewById(R.id.imgClose);
imgClose.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
mCamera.setPreviewCallback(null);
mCamera.setErrorCallback(null);
mCamera.stopPreview();
mCamera.release();
mCamera = null;
System.exit(0);
);
// btn to switch camera
ImageButton imgSwitch = (ImageButton) findViewById(R.id.cameraSwitch);
imgSwitch.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
// switchCamera++;
);
public void SwapCamera()
mCameraView = new CameraView(this, mCamera);//create a SurfaceView to show camera data
FrameLayout camera_view = (FrameLayout)findViewById(R.id.camera_view);
camera_view.addView(mCameraView);//add the SurfaceView to the layout
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults)
switch (requestCode)
case MY_PERMISSIONS_REQUEST_CAMERA:
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED)
// permission was granted, yay! Do the
// camera-related task you need to do.
try
mCamera = Camera.open(1);//you can use open(int) to use different cameras
catch (Exception e)
Log.d("ERROR", "Failed to get camera: " + e.getMessage());
if(mCamera != null)
// mCameraView = new CameraView(this, mCamera);//create a SurfaceView to show camera data
// FrameLayout camera_view = (FrameLayout)findViewById(R.id.camera_view);
// camera_view.addView(mCameraView);//add the SurfaceView to the layout
SwapCamera();
//btn to close the application
ImageButton imgClose = (ImageButton)findViewById(R.id.imgClose);
imgClose.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
mCamera.setPreviewCallback(null);
mCamera.setErrorCallback(null);
mCamera.stopPreview();
mCamera.release();
mCamera = null;
System.exit(0);
);
// btn to switch camera
ImageButton imgSwitch = (ImageButton)findViewById(R.id.cameraSwitch);
imgSwitch.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
// switchCamera++;
);
else
// permission denied, boo! Disable the
// functionality that depends on this permission.
return;
// other 'case' lines to check for other
// permissions this app might request
public void onActivityResult()
【问题讨论】：
【参考方案1】：我相信你缺少“else”
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.CAMERA)
!= PackageManager.PERMISSION_GRANTED)
// your code
else
// stuff with camera
try
mCamera = Camera.open(1);
catch (Exception e)
...
【讨论】：
我很困惑我缺少“else”的地方......我的“try”块使用 onRequestPermissionsResult 方法......我应该将它移到 onCreate 方法吗？ （在“if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED)”区域内） 您应该将其复制到 onCreate 方法。 @Vlad Matvienko 解释道。【参考方案2】：你只在onActivityResult启动摄像人员，只有在你没有权限时才会调用，并请求他们：
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.CAMERA)
!= PackageManager.PERMISSION_GRANTED)
...
这个if 需要else 用于权限已经是PERMISSION_GRANTED 的情况。你必须在这里做和onActivityResult一样的工作人员：
else
try
mCamera = Camera.open(1);//you can use open(int) to use different cameras
catch (Exception e)
Log.d("ERROR", "Failed to get camera: " + e.getMessage());
if(mCamera != null)
// mCameraView = new CameraView(this, mCamera);//create a SurfaceView to show camera data
// FrameLayout camera_view = (FrameLayout)findViewById(R.id.camera_view);
// camera_view.addView(mCameraView);//add the SurfaceView to the layout
SwapCamera();
//btn to close the application
ImageButton imgClose = (ImageButton)findViewById(R.id.imgClose);
imgClose.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
mCamera = null;
System.exit(0);
);
// btn to switch camera
ImageButton imgSwitch = (ImageButton)findViewById(R.id.cameraSwitch);
imgSwitch.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
// switchCamera++;
);
【讨论】：
我已将 try 块复制到 else 语句（就在 != 到 PERMISSION_GRANTED 之外），但我仍然得到相同的结果...我想我误解了你的答案跨度> @fmi，你有什么例外吗？ 不....第一次加载应用程序时，它会提示我请求....然后前置摄像头顶部显示 2 个图标....关闭应用程序后并重新打开，我不再收到提示，我只看到一个白色屏幕，顶部有 2 个图标，不再对触摸做出反应 你能更新你问题中的代码让我看看也许我找到了一些东西。 我刚刚更新了代码，但我注意到我收到了一个警告......我的“addView”调用“可能会产生空指针异常”......它在我的 swapCamera() 方法中以上是关于我的简单相机应用程序（android）在第一次尝试后不会加载相机视图的主要内容，如果未能解决你的问题，请参考以下文章