Question

我想在设备中创建目录和文件。

但是当File.mkdirs（）总是返回false时... 我不知道为什么！

我甚至在清单中添加了这样的权限：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="pkg.pkg.pkg">

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <application
....

这是我的代码：

File directory = null;
File file = null;
String dir = "";
String folderName = "test";

String sdcard = Environment.getExternalStorageState();

if(sdcard.equals(Environment.MEDIA_MOUNTED)){
    dir = Environment.getExternalStorageDirectory().getAbsolutePath();
} else {
    dir = Environment.getRootDirectory().getAbsolutePath();
}

directory = new File(dir, folderName);

if(!directory.exists()) {
    directory.mkdirs(); // return false here.
}

if(directory.isDirectory()){

    file = new File(directory.getAbsolutePath(), fileName);
    if(file.exists()){
        String tempFileName = et_export.getText().toString();

        // Check duplicate file name
        for(int i=1;;i++){
            fileName = tempFileName + " (" + i + ").png";
            file = new File(directory.getAbsolutePath(), fileName);
            if(!file.exists()) break;
        } // for

    } // if(file.exists())

} // if(directory.isDirectory())

问题是什么......？

Answer 1

https://developer.android.com/training/permissions/requesting.html

从Android 6.0（API级别23）开始，用户在应用程序运行时向应用程序授予权限，而不是在安装应用程序时。

您需要手动编写权限授予部分（除了在清单中定义它之外）。

以下是developer.android.com的片段

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

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

        // Show an expanation 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.WRITE_EXTERNAL_STORAGE},
                MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE);

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

android File.mkdirs（）总是返回false

1 个答案: