从“设置”屏幕授予用户更改权限

Question

应用程序需要两个权限：

1. 读电话状态
2. 摄像头

应用程序的屏幕如下：

Screen A: Splash (根据权限状态处理屏幕导航)

屏幕B:权限屏幕(如果用户没有授予电话权限)

屏幕C:条款和条件

启动时，App将检查是否授予了电话许可。如果获得批准，应用程序将打开屏幕C，否则它将保持在相同的屏幕B。

步骤：

1. 打开App -> Splash ->权限屏幕
2. 单击“授予权限”->权限对话框->拒绝权限
3. 点击“打开设置”
4. 批准“照相机”许可(不是电话许可)
5. 点击设备的'Back‘按钮，然后返回到app。
6. 权限屏幕将显示为不授予'phone'权限。
7. 再次重复步骤2和3
8. 现在删除‘相机’许可，并授予‘手机’许可(因为我们已经改变相机权限应用程序进程将被杀死，并重新启动)。
9. 重复步骤5，飞溅，然后屏幕C(条款和条件)将显示。
10. 再次点击‘后退’按钮，将显示相同的屏幕C(屏幕C在后台堆栈中有两个实例)

我可以使用'CLEAR_TASK'和'CLEAR_TOP'标志和startActivity，目的是了解当用户更改、设置权限时应用程序发生了什么变化。

Observation:

1. 当用户授予权限时，我们的应用程序将没有任何效果。
2. 当用户删除授予的权限时，安卓应用程序将杀死并重新启动应用程序。(如果正在发生这种情况，那么为什么会出现两个T&C屏幕的实例？)

我在这里有点困惑！！

Answer 1

@AndiGeeky这里是一些完整的代码，如果选择了允许或拒绝，它就会通知用户，并且它将管理另外两种情况--用户被选中永远不要再问，或者用户在被允许不允许之后是否更改了设置

       if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if (checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
            //.... write file into storage ...
            System.out.println("SDK > BuildVersion TRUE");
        } else {
            requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 666);  // Comment 26
            System.out.println("go to requestPermissions");
        }
    }
    onLoad();
}

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {

    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    switch (requestCode) {

        case 666: // Allowed was selected so Permission granted
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                Snackbar s = Snackbar.make(findViewById(android.R.id.content),"Permission Granted",Snackbar.LENGTH_LONG);
                View snackbarView = s.getView();
                TextView textView = (TextView) snackbarView.findViewById(android.support.design.R.id.snackbar_text);
                textView.setTextColor(Color.RED);
                textView.setTextSize(18);
                textView.setMaxLines(6);
                s.show();

                // do your work here

            } else if (Build.VERSION.SDK_INT >= 23 && !shouldShowRequestPermissionRationale(permissions[0])) {
                // User selected the Never Ask Again Option Change settings in app settings manually
                AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
                alertDialogBuilder.setTitle("Change Permissions in Settings");
                alertDialogBuilder
                        .setMessage("" +
                                "\nClick SETTINGS to Manually Set\n"+"Permissions to use Database Storage")
                        .setCancelable(false)
                        .setPositiveButton("SETTINGS", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
                                Uri uri = Uri.fromParts("package", getPackageName(), null);
                                intent.setData(uri);
                                startActivityForResult(intent, 1000);     // Comment 3.
                            }
                        });

                AlertDialog alertDialog = alertDialogBuilder.create();
                alertDialog.show();

            } else {
                    // User selected Deny Dialog to EXIT App ==> OR <== RETRY to have a second chance to Allow Permissions
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_DENIED) {

                    AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
                    alertDialogBuilder.setTitle("Second Chance");
                    alertDialogBuilder
                            .setMessage("Click RETRY to Set Permissions to Allow\n\n"+"Click EXIT to the Close App")
                            .setCancelable(false)
                            .setPositiveButton("RETRY", new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog, int id) {
                                    //ActivityCompat.requestPermissions((Activity) context, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, Integer.parseInt(WRITE_EXTERNAL_STORAGE));
                                    Intent i = new Intent(MainActivity.this,MainActivity.class);
                                    i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);
                                    startActivity(i);
                                    }
                            })
                            .setNegativeButton("EXIT", new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog, int id) {
                                    finish();
                                    dialog.cancel();
                                }
                            });
                    AlertDialog alertDialog = alertDialogBuilder.create();
                    alertDialog.show();
                }
            }
            break;
    }};

Answer 2

/**** If user changes, permission from settings it will again ask for permission to 
      granted.You should always check if user changes permission from settings
      using below code ***/ 

if(checkSelfPermission(Manifest.permission.your_permission_name) == PackageManager.PERMISSION_GRANTED)