java - Android请求运行时权限不起作用

Question

尝试在 Android 模拟器上请求运行时权限时遇到了一些问题。我要做的是在单击按钮后，请求读取和写入外部存储权限，然后再转到我的异步任务类。

这是我的代码：

private static final int PERMISSION_REQUEST_CODE = 1;
String readPermission = Manifest.permission.READ_EXTERNAL_STORAGE;
String writePermission = Manifest.permission.WRITE_EXTERNAL_STORAGE;
@Click(R.id.buttonVersionUpgrade)
void buttonVersionUpgradeClicked(View v) {

    if (!checkPermission(readPermission) || !checkPermission(writePermission)) {
        requestPermission(readPermission);
        requestPermission(writePermission);
    }
   // async task here
}

private boolean checkPermission(String permission){
    if (Build.VERSION.SDK_INT >= 23) {
        int result = ContextCompat.checkSelfPermission(getApplicationContext(), permission);
        if (result == PackageManager.PERMISSION_GRANTED){
            return true;
        } else {
            return false;
        }
    } else {
        return true;
    }
}

private void requestPermission(String permission){
    if (ActivityCompat.shouldShowRequestPermissionRationale(this, permission)){
        Toast.makeText(getApplicationContext(), "Read/Write external storage permission allows us to read/write data. Please allow in App Settings for additional functionality.",Toast.LENGTH_LONG).show();
    }
    ActivityCompat.requestPermissions(this, new String[]{permission},PERMISSION_REQUEST_CODE);
}

@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
    switch (requestCode) {
        case PERMISSION_REQUEST_CODE:
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(getApplicationContext(), "Permission Granted. Now you can read/write data.",
                        Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(getApplicationContext(),"Permission Denied. You cannot read/write data.",
                        Toast.LENGTH_LONG).show();
            }
            break;
    }
}

但是，它不会在移动到异步任务执行之前提示用户提供权限，这会导致应用程序崩溃。它仅在应用程序崩溃时提示用户。有任何想法吗？

谢谢！

标签： javaandroidpermissions

Answer 1

这是因为ActivityCompat.requestPermissions不是同步调用。操作系统将显示弹出窗口（实际上是一个 Activity），然后执行它后面的语句。

由于这两个权限对于您的请求都是强制性的，因此它们同时是必需的。

 if (!checkPermission(readPermission) || !checkPermission(writePermission)) {
        requestPermission(new String[] {readPermission,writePermission});        
  } else{
    //Run Async task directly since the permissions are already granted
  }



private void requestPermission(String[] permissions){
    if (ActivityCompat.shouldShowRequestPermissionRationale(this, permissions[0])||ActivityCompat.shouldShowRequestPermissionRationale(this, permissions[1])){
        Toast.makeText(getApplicationContext(), "Read/Write external storage permission allows us to read/write data. Please allow in App Settings for additional functionality.",Toast.LENGTH_LONG).show();
    }
    ActivityCompat.requestPermissions(this, permissions,PERMISSION_REQUEST_CODE);
}

ActivityCompat.requestPermissions(this, permissions, requestCode);

将AsyncTask执行移至onRequestPermissionsResult如下：

@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
    switch (requestCode) {
        case PERMISSION_REQUEST_CODE:
            if (verifyGrantResults(grantResults)) {
                Toast.makeText(getApplicationContext(), "Permission Granted. Now you can read/write data.",
                        Toast.LENGTH_LONG).show();
                        //start Async Task here
            } else {
                Toast.makeText(getApplicationContext(),"Permission Denied. You cannot read/write data.",
                        Toast.LENGTH_LONG).show();
            }
            break;
    }
}

private boolean verifyGrantResults(final int[] grantResults) {
        boolean permissionsGranted = true;
        if (grantResults.length > 0) {
            for (int result : grantResults) {
                if (result == PackageManager.PERMISSION_DENIED) {
                    permissionsGranted = false;
                }
            }
            return permissionsGranted;
        }
        return false;
    }