Android 6（M）权限问题（创建目录不起作用）

Question

我有这个代码用于创建保存图片的目录：

        File storageDir = null;
        if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {                
            storageDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "myphoto");
            if (!storageDir.mkdirs()) {                    
                if (!storageDir.exists()){                       
                    Log.d("photo", "failed to create directory");
                    return null;
                }
            }
        }
        return storageDir;

storeDir 在android 6下面返回"/storage/emulated/0/Pictures/myphoto/"，在android 6上返回null。

我有权限<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

buildToolVersion 23 targetSdkVersion 23

如何解决？

Answer 1

正如@CommonsWare所回答，Android M上有运行时权限询问概念，所以在新方法中，安装应用程序时不会询问权限，而是在运行时尝试使用请求权限的手机的特定功能时。用户以后也可以禁用phone settings->app->yourapp->permissions的权限。所以你必须先检查一下这个权限，然后问用户：

int REQUEST_WRITE_EXTERNAL_STORAGE=1;
////...
        File storageDir = null;
        if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
            //RUNTIME PERMISSION Android M
            if(PackageManager.PERMISSION_GRANTED==ActivityCompat.checkSelfPermission(context,Manifest.permission.WRITE_EXTERNAL_STORAGE)){
                storageDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "myPhoto");
            }else{
                requestPermission(context);
            }    

        } 
        return storageDir;
////...
        private static void requestPermission(final Context context){
        if(ActivityCompat.shouldShowRequestPermissionRationale((Activity)context,Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
            // Provide an additional rationale to the user if the permission was not granted
            // and the user would benefit from additional context for the use of the permission.
            // For example if the user has previously denied the permission.

            new AlertDialog.Builder(context)
                    .setMessage(context.getResources().getString(R.string.permission_storage))
                    .setPositiveButton(R.string.tamam, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    ActivityCompat.requestPermissions((Activity) context,
                            new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                            REQUEST_WRITE_EXTERNAL_STORAGE);
                }
            }).show();

        }else {
            // permission has not been granted yet. Request it directly.
            ActivityCompat.requestPermissions((Activity)context,
                    new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                    REQUEST_WRITE_EXTERNAL_STORAGE);
        }
    }

///...

    @Override
    public void onRequestPermissionsResult(int requestCode,String permissions[], int[] grantResults) {
        switch (requestCode) {
            case UtilityPhotoController.REQUEST_WRITE_EXTERNAL_STORAGE: {
                if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    Toast.makeText(context,
                            getResources().getString(R.string.permission_storage_success),
                            Toast.LENGTH_SHORT).show();

                } else {
                    Toast.makeText(context,
                            getResources().getString(R.string.permission_storage_failure),
                            Toast.LENGTH_SHORT).show();
                    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
                }
                return;
            }
        }
    }

Answer 2

您在Android 6.0+环境中运行此功能，并且targetSdkVersion为23。

在这种情况下，WRITE_EXTERNAL_STORAGE是the Android 6.0 runtime permission system的一部分。修改您的应用以参与此系统，或将您的targetSdkVersion放在23以下。

Answer 3

您必须获得此项工作的许可，例如：

for it it impliment this code：

 if (ContextCompat.checkSelfPermission(this,
            Manifest.permission.WRITE_EXTERNAL_STORAGE)
            != PackageManager.PERMISSION_GRANTED) {

        if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                Manifest.permission.WRITE_EXTERNAL_STORAGE)) {

        } else {


            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},23
                    );
        }
    }

祝你好运!!!

Answer 4

试试这段代码。

library(ggplot2)
library(dplyr)
library(tidyr)

dfr <- data.frame(x=factor(1:20),y1=runif(n=20)) %>%
        mutate(y2=1-y1) %>%
        gather(variable,value,-x)


ggplot(dfr,aes(x=x,y=value,fill=variable))+
  geom_bar(stat="identity")+
  theme(legend.position="top",
        legend.justification="right")