mkdirs() 使用外部写入权限返回 false

Question

我的 mkdirs 函数有问题。查看我的权限清单

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="xxxxxx"
android:versionCode="15"
android:versionName="3.1.1508">

<!-- Global permissions -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

还有我的代码

String APP_PATH_SD_CARD = "/xxxxx";
    String fullPath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES) + APP_PATH_SD_CARD;

    if(!Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())){
        ToastDressmup.make(this, "External SD card not mounted", 0, ToastAction.CLOSE.getValue()).show();
    }

    try {
        File dir = new File(fullPath);
        if (!dir.exists()) {
            dir.mkdirs();
        }

        ==> My file doesn't exist

SD 卡已安装。我不明白。我在互联网上阅读了很多答案，但仍然是错误的。

我在模拟器（使用模拟 SD 卡）和 Nexus 5 上进行了测试，但它不起作用。在我的 HTC One X 上它可以工作，为什么？！我很绝望

谢谢大家！ G.

Answer 1

在 cmets 中已解决，答案是缺少权限。

自 Android 6 起，权限处理发生了变化，如下所述：

Exception 'open failed: EACCES (Permission denied)' on Android

或

Android permission doesn't work even if I have declared it

您需要在运行时再次收集这些权限：

引用第一个答案：

/**
 * Checks if the app has permission to write to device storage
 *
 * If the app does not has permission then the user will be prompted to grant permissions
 *
 * @param activity
 */
public static void verifyStoragePermissions(Activity activity) {
    // Check if we have write permission
    int permission = ActivityCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE);

    if (permission != PackageManager.PERMISSION_GRANTED) {
        // We don't have permission so prompt the user
        ActivityCompat.requestPermissions(
                activity,
                PERMISSIONS_STORAGE,
                REQUEST_EXTERNAL_STORAGE
        );
    }
}