Question

我正在构建一个需要用户位置的应用。我正在关注here的Android培训文档，其中包含：

shouldShowRequestPermissionRationale返回布尔值，指示我们是否应该显示具有请求权限的理由的UI（危险权限，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.
    }
}

[我的怀疑]不应该是这段代码（下面）

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

进入＆＃39;如果＆＃39;条件在这里..

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

}

我的意思是，如果

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

是真的，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。一个例子将非常感激。

注意：当然，我在Android M上运行我的应用，我的目标sdk是＆gt; = 23。

Answer 1

根据文档，

shouldShowRequestPermissionRationale返回布尔值，指示是否＆gt;我们应该显示具有请求权限的理由的UI。

此UI是我们的自定义UI（例如，我们可以显示alertdialog），而不是我们设备显示的对话框（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。

另请注意，

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

因此，总结一下

shouldShowRequestPermissionRationale仅在应用程序先前启动且用户“拒绝”权限而不检查“永不再询问”时才返回true。
在其他情况下（第一次推出的应用，或之前推出的应用，用户通过选中“永不再问”来拒绝权限），返回值为false。

<强>实施

让我们创建一个PermissionUtils.java文件，为我们处理不同的案例。

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();
            }
        }
    }
}

<强>逻辑

我们首先检查是否首先要求运行时权限？这可以通过以下方式完成：
```
if (!isRuntimePermissionRequired()) {...}
```
如果我们确实需要运行时权限，那么我们检查是否已经通过
获得了该权限
```
ContextCompat.checkSelfPermission(activity, permission) != PackageManager.PERMISSION_GRANTED)
```

如果我们没有这个权限，那么我们需要处理两个案例：

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：

在我们的PermissionUtils.java中，我们有一个定义的接口，其中包含5个抽象方法。这些方法是将在不同情况下调用的回调，如上所述。

最后在我们的活动中，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();


                }
            });


}

希望这有帮助。

Answer 2

另一种选择是使用由Google自己提供的 EasyPermissions ，如“简化Android M系统权限”。然后，您无需直接致电shouldShowRequestPermissionRationale。

然后您不必直接调用shouldShowRequestPermissionRationale或处理其返回值。

Answer 3

请求权限有两个阶段 - 显示基本原理，然后实际请求权限。

它们通常表现为按顺序显示的两个单独的对话框：

一个对话框，其中只包含文本，向用户提供所需权限的原因（理由）
实际请求权限的对话框。如下图所示：

因此文档中的代码是正确的。逻辑是：

if we need to show a rationale:
    show the rationale dialog
otherwise:
    just ask for permissions to be granted without showing the rationale dialog

shouldShowRequestPermissionRationale和requestPermissions之间有什么区别？

3 个答案: