android - shouldShowRequestPermissionRationale 和 requestPermissions 之间有什么区别？

Question

我正在构建一个需要用户位置的应用程序。我正在关注来自 here 的 Android 培训文档其中说:

shouldShowRequestPermissionRationale return the boolean indicating whether or not we should show UI with rationale for requesting a permission (dangerous permission, ACCESS_FINE_LOCATION)

现在在这段代码中(取自文档本身):

if (ContextCompat.checkSelfPermission(thisActivity,
                Manifest.permission.READ_CONTACTS)
        != PackageManager.PERMISSION_GRANTED) {

    // Should we show an explanation?
    if (ActivityCompat.shouldShowRequestPermissionRationale(thisActivity,
            Manifest.permission.READ_CONTACTS)) {

        // 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(thisActivity,
                new String[]{Manifest.permission.READ_CONTACTS},
                MY_PERMISSIONS_REQUEST_READ_CONTACTS);

        // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
        // app-defined int constant. The callback method gets the
        // result of the request.
    }
}

[我的疑问] 这部分代码(下面)不应该

ActivityCompat.requestPermissions(thisActivity,
                new String[]{Manifest.permission.READ_CONTACTS},
                MY_PERMISSIONS_REQUEST_READ_CONTACTS);

在此处的“if”条件内..

 if (ActivityCompat.shouldShowRequestPermissionRationale(thisActivity,
            Manifest.permission.READ_CONTACTS)) {
    //HERE .....

}

我的意思是，如果

ActivityCompat.shouldShowRequestPermissionRationale(thisActivity, Manifest.permission.READ_CONTACTS)   

为真，那么我们需要显示UI，我们将通过

显示UI

ActivityCompat.requestPermissions(thisActivity,
    newString[{Manifest.permission.READ_CONTACTS}, MY_PERMISSIONS_REQUEST_READ_CONTACTS);

请解释我错在哪里。我被困在这里。提前致谢。一个例子将不胜感激。

注意:当然，我在 Android M 上运行我的应用程序，我的目标 sdk 是 >=23。

Answer 1

根据文档，

shouldShowRequestPermissionRationale return the boolean indicating whether >or not we should show UI with rationale for requesting a permission.

此 UI 是我们的自定义 UI(例如，我们可以显示一个警报对话框)，而不是我们的设备显示的对话框(见下文):

Allow SnazzyApp to access your contacts ? //this is NOT our custom UI

考虑到这一点，现在

shouldShowRequestPermissionRationale 的返回值如流程图所示。

还要注意的是，

When that user "denies"  your permission by CHECKING "never ask again", ``shouldShowRequestPermissionRationale`` would still return ``false``. 

总结一下

• shouldShowRequestPermissionRationale 仅当应用程序较早启动并且用户“拒绝”权限而未选中“不再询问”时才会返回 true。
• 在其他情况下(应用程序首次启动，或者应用程序也较早启动并且用户通过选中“不再询问”拒绝许可)，返回值为 false。

实现

让我们创建一个 PermissionUtils.java 文件来为我们处理不同的情况。

public class PermissionUtils {

    private static final String TAG = "PermissionUtils";

    /*
        Inside this shared_preference file, we will just store information
        about whether the user had visited our app earlier or not.
    */

    private static final String PREFS_FILE_NAME = "preference_permission";
    private static final String PREFS_FIRST_TIME_KEY = "is_app_launched_first_time";


    //an interface containing 5 methods
    //...the scenario in which these callback will be called is written below each method declaration.
    public interface PermissionAskListener {


        void onPermissionGranted();
        /*
            User has already granted this permission
            The app must had been launched earlier and the user must had "allowed" that permission
         */


        void onPermissionRequest();
        /*
            The app is launched FIRST TIME..
            We don't need to show additional dialog, we just request for the permission..

         */


        void onPermissionPreviouslyDenied();
        /*
            The app was launched earlier and the user simply "denied" the permission..
            The user had NOT clicked "DO NOT SHOW AGAIN"
            We need to show additional dialog in this case explaining how "allowing this permission" would be useful to the user
         */


        void onPermissionDisabled();
        /*
            The app had launched earlier and the user "denied" the permission..
            AND ALSO had clicked "DO NOT ASK AGAIN"
            We need to show Toask/alertdialog/.. to indicate that the user had denied the permission by checking do not disturb too...
            So, you might want to take the user to setting>app>permission page where the user can allow the permission..


         */

    }

    // preference utility methods
    private static boolean getApplicationLaunchedFirstTime(Activity activity) {
        SharedPreferences sharedPreferences = activity.getSharedPreferences(PREFS_FILE_NAME, MODE_PRIVATE);
        return sharedPreferences.getBoolean(PREFS_FIRST_TIME_KEY, true);
    }

    private static void setApplicationLaunchedFirstTime(Activity activity) {
        SharedPreferences sharedPreferences = activity.getSharedPreferences(PREFS_FILE_NAME, MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putBoolean(PREFS_FIRST_TIME_KEY, false);
        editor.commit();
    }


    private static boolean isRuntimePermissionRequired() {
        return (Build.VERSION.SDK_INT >= 23);
    }

    public static void checkPermission(Activity activity, String permission, PermissionAskListener permissionAskListener) {

        Log.d(TAG, "checkPermission");


        if (!isRuntimePermissionRequired()) {
            /*
                Runtime permission not required,
                THE DEVICE IS RUNNING ON < 23, So, no runtime permission required..
                Simply call **** permissionAskListener.onPermissionGranted() ****
             */


            permissionAskListener.onPermissionGranted();
        } else {
            //runtime permission required here...

            //check if the permission is already granted, i.e the application was launched earlier too, and the user had "allowed" the permission then.
            if (ContextCompat.checkSelfPermission(activity, permission) != PackageManager.PERMISSION_GRANTED) {
                /* We don't have permission, two cases arise:
                     1. App launched first time, 
                     2. App launched earlier too, and the user had denied the permission is last launch
                           2A. The user denied permission earlier WITHOUT checking "Never ask again"
                           2B. The user denied permission earlier WITH checking "Never ask again"
                */

                if (ActivityCompat.shouldShowRequestPermissionRationale(activity, permission)) {

                    /* 
                       shouldShowRequestPermissionRationale returned true
                       this means Case: 2A
                       see the flowchart, the only case when shouldShowRequestPermissionRationale returns "true", is when the application was launched earlier too and the user had "denied" the permission in last launch WITHOUT checking "never show again"
                    */

                    permissionAskListener.onPermissionPreviouslyDenied();
                } else {
                    /*  
                         this means, either - 
                         Case: 1 or Case 2B
                         See Flowchart, shouldShowRequestPermissionRationale returns false, only when app is launched first time (Case: 1) or app was launched earlier too and user HAD checked "Never show again" then (Case: 2B)
                    */
                    if (getApplicationLaunchedFirstTime(activity)) {

                        //Case: 1
                        Log.d(TAG, "ApplicationLaunchedFirstTime");

                        setApplicationLaunchedFirstTime(activity);  //  ** DON'T FORGET THIS **
                        permissionAskListener.onPermissionRequest();

                    } else {
                        //Case: 2B
                        Log.d(TAG, "onPermissionDisabled");

                        permissionAskListener.onPermissionDisabled();
                    }
                }


            } else {
                Log.d(TAG, "Permission already granted");

                permissionAskListener.onPermissionGranted();
            }
        }
    }
}

逻辑

1. 我们首先检查我们是否需要运行时许可？这是由以下人员完成的:

   if (!isRuntimePermissionRequired()) {...}
   

2. 如果我们确实需要运行时权限，那么我们会检查我们之前是否已经获得该权限

   ContextCompat.checkSelfPermission(activity, permission) != PackageManager.PERMISSION_GRANTED)
   

3. 如果我们没有权限，那么我们需要处理两种情况:

   1. App launched first time, 
   2. App launched earlier too, and the user had denied the permission is last launch                  
       2A. The user denied permission earlier WITHOUT checking "Never ask again".
       2B. The user denied permission earlier WITH checking "Never ask again".
   

因此，底线是:

Inside our PermissionUtils.java, we have an defined an interface which contains 5 abstract methods. These methods are the callbacks which will be called in different cases as discussed above.

最后，在我们的 Activity 中，我们通过实现监听器的回调来处理所有这些情况。

    PermissionUtils.checkPermission(MainActivity.this,
            Manifest.permission.ACCESS_FINE_LOCATION,
            new PermissionUtils.PermissionAskListener() {
                @Override
                public void onPermissionGranted() {
                    updateUI();

                }

                @Override
                public void onPermissionRequest() {

                    ActivityCompat.requestPermissions(MainActivity.this,
                            new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                            My_PERMISSION_ACCESS_FINE_LOCATION);


                }

                @Override
                public void onPermissionPreviouslyDenied() {

                    //Show an alert message and "request the permission" in its "setPositiveButton"
                    //...and in "setOnNegativeButton", just cancel the dialog and do not run the
                    //...functionality that requires this permission (here, ACCESS_FINE_LOCATION)
                    new AlertDialog.Builder(MainActivity.this)
                            .setTitle("Permission required")
                            .setMessage("Location is required for this application to work ! ")
                            .setPositiveButton("Allow", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    ActivityCompat.requestPermissions(MainActivity.this,
                                            new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                                            My_PERMISSION_ACCESS_FINE_LOCATION);


                                }

                            })
                            .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    dialog.cancel();
                                    finish();
                                }
                            })
                            .show();


                }

                @Override
                public void onPermissionDisabled() {



                    new AlertDialog.Builder(MainActivity.this)
                            .setTitle("Permission Disabled")
                            .setMessage("Please enable the permission in \n  Settings>Uber>Permission \n and check 'location' permission")
                            .setPositiveButton("Go to settings", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    startActivity(new Intent(Settings.ACTION_SETTINGS));


                                }

                            })
                            .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    dialog.cancel();
                                    finish();
                                }
                            })
                            .show();


                }
            });


}

希望这对您有所帮助。