从SD卡读取

Question

I am trying to read a simple text file from my SD card using Java, and I can't seem to be able to open it. I am using Eclipse for Mobile Developers on Ubuntu 12.04. Here's the code in the onCreate() method of the main activity:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    String status = "Hello, is it me you're looking for?";
    String storageState = Environment.getExternalStorageState();

    File dir = Environment.getExternalStorageDirectory();
    File f = new File(dir, "textTest.txt");

    if (f.exists()) {
        status = "File is found!";
    } else {
        status = "File is not found!";
    }

    this.text1 = (TextView) findViewById(R.id.textView1);
    text1.setText(status.subSequence(0, status.length()));
}

Also, here are some of the constructors I tried for File f , none of them worked:

File f = new File(dir, "textTest.txt");
File f = new File("/sdcard/textTest.txt");
File f = new File(dir, "mnt/sdcard/textTest.txt");

Finally, I checked the external storage state using the storageState string above, and the value returned by Environment.getExternalStorageState() is mounted . The only lead I have is I think there might be something to do with whether the SD card is readable or not, but that's just a guess. Any ideas?

Added: In case you haven't guessed, the TextView object reads " File not found! " when I launch the activity.

Added 2: Ok, I just tried something that worked. When I connect the phone via USB, two folders related to the phone open: one which has all of the folders from the internal storage (data, DCIM... etc) and the folder which I assume is connected to the SD card, since I added the files through my laptop card reader and then input it into the phone. However, when I copy the file "testText.txt" into the first folder (which I assumed is related to the internal storage), the constructor File f = new File("/sdcard/textTest.txt"); works. Howcome?

Answer 1

Based on comments..

Add this to your AndroidManifest.xml

android.permission.READ_EXTERNAL_STORAGE

Also if you do somethings with WRITE operation add this permission

android.permission.WRITE_EXTERNAL_STORAGE