为什么我的应用程序显示两个 requestPermissionRationales？答案

【问题标题】：Why is my application displaying two requestPermissionRationales?为什么我的应用程序显示两个 requestPermissionRationales？
【发布时间】：2018-09-24 09:56:40
【问题描述】：

我对编程比较陌生，刚刚制作了一个相机应用程序，其预览窗口位于表面视图中，需要访问位置，显然需要访问相机。

但是，在显示requestPermissionRationale 以获得许可并在用户同意之后，会出现第二个requestPermissionRationale，将相机预览冻结在适当的位置。预览在离开应用程序并返回时起作用。为什么会这样？

我已经包含了请求权限的方法、我的 surfaceview 类和下面的 logcat。 requestUpdates() 包括实例化相机的代码，surfaceview.request() 在onCreate() 中被调用。如下图，在onResume()中调用request，在onCreate()中也调用。

   private void showMessageOKCancel(String message, DialogInterface.OnClickListener okListener) {
        new AlertDialog.Builder(MainActivity.this)
                .setMessage(message)
                .setPositiveButton("OK", okListener)
                .setNegativeButton("Cancel", null)
                .create()
                .show();
    }
 @TargetApi(23)
    protected void requestCam() {
        if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.CAMERA)) {
            showMessageOKCancel("This app requires access to the camera in order to function.",
                    new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            requestPermissions(new String[] {Manifest.permission.CAMERA}, CAMPERMISSION_KEY);
                        }
                    });

        } else {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, CAMPERMISSION_KEY);
        }

    }
    @TargetApi(23)
    protected void requestLoc() {
        if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.ACCESS_FINE_LOCATION)) {

            showMessageOKCancel("This app requires access to the location in order to function.",
                    new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            requestPermissions(new String[] {Manifest.permission.ACCESS_FINE_LOCATION}, LOCPERMISSION_KEY);
                        }

                    });

        } else {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, LOCPERMISSION_KEY);
        }
    }
    @TargetApi(23)
    protected void requestBoth() {
        if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.ACCESS_FINE_LOCATION) && ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.CAMERA)) {
            showMessageOKCancel("This app requires access to both the location and the camera in order to function.",
                    new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                           requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.CAMERA}, MULT_KEY);
                           requestPermissions(new String[] {Manifest.permission.CAMERA}, CAMPERMISSION_KEY);
                        }
                    });

        } else {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.CAMERA}, MULT_KEY);
        }

    }
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        boolean needLoc = ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED;
        boolean needCam = ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED;
        switch (requestCode) {
            case LOCPERMISSION_KEY:
                if (needLoc == false && needCam == false) {
                    requestUpdates();
                } else {
                    request();
                }
                break;
            case CAMPERMISSION_KEY:
                if (needCam == false && needLoc == false) {
                    requestUpdates();

                } else {
                    request();
                }
                break;
            case MULT_KEY:
                if (needLoc == false && needCam == false) {
                    requestUpdates();

                } else {
                    request();
                }
        }
    }
    @TargetApi(23)
    public void request() {
        if ((ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) && (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED)) {
            requestUpdates();
        } else if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            requestCam();
        } else if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) {
            requestLoc();
        } else {
            requestBoth();
        }
    }

public void onResume() {
 request();
}
04-13 21:31:33.328 30847-30847/danielwei816.com.danger W/System.err: java.io.IOException: setPreviewTexture failed
04-13 21:31:33.328 30847-30847/danielwei816.com.danger W/System.err:     at android.hardware.Camera.setPreviewSurface(Native Method)
04-13 21:31:33.328 30847-30847/danielwei816.com.danger W/System.err:     at android.hardware.Camera.setPreviewDisplay(Camera.java:738)
04-13 21:31:33.328 30847-30847/danielwei816.com.danger W/System.err:     at danielwei816.com.danger.ImageSurfaceView.surfaceCreated(ImageSurfaceView.java:29)
04-13 21:31:33.328 30847-30847/danielwei816.com.danger W/System.err:     at android.view.SurfaceView.updateWindow(SurfaceView.java:634)
04-13 21:31:33.328 30847-30847/danielwei816.com.danger W/System.err:     at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:162)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:944)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2281)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1299)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6558)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:871)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.view.Choreographer.doCallbacks(Choreographer.java:683)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.view.Choreographer.doFrame(Choreographer.java:619)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:857)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.os.Handler.handleCallback(Handler.java:751)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:95)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.os.Looper.loop(Looper.java:154)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:6316)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:872)
04-13 21:31:33.329 30847-30847/danielwei816.com.danger W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:762)
04-13 21:31:33.387 30847-30847/danielwei816.com.danger E/Camera: Error 2

【问题讨论】：

您能否更新您的代码，指出您在哪里调用方法requestCam()、requestLoc()、requestBoth()？你是在onResume() 或onStart() 上做的吗？
我更新了它。这些方法是通过 request() 方法实现的，该方法在 onResume() 和 onCreate() 中调用。

标签： java android android-camera android-permissions

【解决方案1】：

首先，您的代码中存在逻辑错误。您的权限检查和权限请求不匹配。请代码中的cmets：

   public void request() {
        if ((ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) && (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED)) {
            requestUpdates();
        } else if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
//You are checking for Location permission grant status but requesting camera permission
            requestCam();
        } else if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) {
//You are checking for Camera permission grant status but requesting location permission
            requestLoc();
        } else {
            requestBoth();
        }
    }

您看到以下两个理由的原因：

您正在onResume() 中请求权限。

当您请求权限时，Android 操作系统会在内部启动一个新 Activity 以显示权限对话框并覆盖您当前的 Activity。当用户授予权限时，您的活动将进入前台并调用onResume()。结果你会看到另一个理由

您可以通过仅检查和请求（如有必要）onCreate() 中的权限并仅在授予权限后触发访问相机的请求来避免它。

【讨论】：

【解决方案2】：

尝试以这种方式实现（即，使用单个语句来请求权限）

@TargetApi(23)
protected void requestBoth() {
    if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.ACCESS_FINE_LOCATION) && ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.CAMERA)) {
        showMessageOKCancel("This app requires access to both the location and the camera in order to function.",
                new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                       requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.CAMERA}, MULT_KEY);
                       // requestPermissions(new String[] {Manifest.permission.CAMERA}, CAMPERMISSION_KEY);
                    }
                });

    } else {
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.CAMERA}, MULT_KEY);
    }

}

【讨论】：