Question

我需要打开图库以在特定目录中显示图像，在我按照此搜索后进行搜索 How to open gallery to show images in a specific directory

但是file.list在android 4.4上返回一个null String [] 比我写一些测试代码：

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    listDirectory("ExternalStorageRoot",
            Environment.getExternalStorageDirectory());
    listDirectory(
            "DCIM",
            Environment
                    .getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM));
    writeFileTest();

}

private void writeFileTest() {
    String tag = "WriteTest";
    String path = Environment.getExternalStoragePublicDirectory(
            Environment.DIRECTORY_PICTURES).getAbsolutePath();
    path = path + "/testFile.txt";
    Log.d(tag, "path : " + path);

    File file=new File(path);

    FileOutputStream fileOutputStream;
    try {
        fileOutputStream = new FileOutputStream(file);      
        fileOutputStream.write("THIS IS A TEST LINE".getBytes());
        fileOutputStream.flush();
        fileOutputStream.close();

    } catch (IOException e) {
        e.printStackTrace();
    }


}

private void listDirectory(String tag, File f) {
    Log.d(tag, "absolute path " + f.getAbsolutePath());
    Log.d(tag, "is dir " + f.isDirectory());
    Log.d(tag, "can read " + f.canRead());
    Log.d(tag, "can write " + f.canWrite());

    String[] fileNames = f.list();

    Log.d(tag, fileNames == null ? "fileNames is null"
            : "fileNames is not null");

    if (fileNames != null) {
        for (String string : fileNames) {
            Log.d(tag, "file -- " + string);
        }
    }
}

我还在AndroidManifest.xml中添加了这些行

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

编辑：我搞砸了这个许可。现在一切都运转正常！

Answer 1

4.4更改了SD卡的文件权限。你不能再写在个人目录之外了。另见：http://www.androidcentral.com/kitkat-sdcard-changes

如何在android 4.4上读写文件？

1 个答案: