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我们在处理缓存的时候，并不是每次都会在应用私有存储空间那里保存，很多时候是需要用到ExternalStorage。我们平时一般都是用Environment.getExternalStorageDirectory()，这在6.0以前一直是好的，（即使不对，那你的问题应该是没注意加权限，或者是格式不对之类又或者sdcard被移走了等等）。但是到了6.0以后，就发现怎么都不无法创建文件了。很多人就疑惑，该加的权限都加了，怎么就没法创建呢？
原因是Android 6.0以后，google升级了Android的权限管理机制，对于一些敏感的权限，需要显性申请并被用户允许才可能运行。
private void checkPermission() {
if (Build.VERSION.SDK_INT >= 23) {
int write = checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE);
int read = checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE);
if (write != PackageManager.PERMISSION_GRANTED || read != PackageManager.PERMISSION_GRANTED) {
requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE}, 300);
} else {
String name = "CrashDirectory";
File file1 = new File(Environment.getExternalStorageDirectory(), name);
if (file1.mkdirs()) {
Log.i("wytings", "permission -------------> " + file1.getAbsolutePath());
} else {
Log.i("wytings", "permission -------------fail to make file ");
}
}
} else {
Log.i("wytings", "------------- Build.VERSION.SDK_INT < 23 ------------");
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
if (requestCode == 300) {
Log.i("wytings", "--------------requestCode == 300->" + requestCode + "," + permissions.length + "," + grantResults.length);
} else {
Log.i("wytings", "--------------requestCode != 300->" + requestCode + "," + permissions + "," + grantResults);
}
}
备注：附上android的权限组，因为同一组的任何一个权限被授权了，其他权限也自动被授权。例如，一旦WRITE_EXTERNAL_STORAGE被授权了，app也有READ_EXTERNAL_STORAGE.所以，你只申请一个就可以了。
android.permission-group.CALENDAR |
|
android.permission-group.CAMERA |
|
android.permission-group.CONTACTS |
|
android.permission-group.LOCATION |
|
android.permission-group.MICROPHONE |
|
android.permission-group.PHONE |
|
android.permission-group.SENSORS |
|
android.permission-group.SMS |
|
android.permission-group.STORAGE |
|
Android 中 Environment.getExternalStorageDirectory()无效
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原文地址：http://www.cnblogs.com/wytings/p/5226101.html
