将文件写入SD卡不起作用

Question

I wrote this to store a file in SD card, but it's not working.

public class TestarFilesActivity extends Activity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        File root = Environment.getExternalStorageDirectory();

        try {
            if (root.canWrite()) {
                File file = new File(root, "agora.txt");
                FileWriter fwriter = new FileWriter(file);
                BufferedWriter out = new BufferedWriter(fwriter);
                out.write("Hello world");
                out.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }TestarFilesActivity.this.finish();
    }
}

How is this problem caused and how can I solve it? I think it's everything right and I have write the permission in the manifest too.

Answer 1

检查报告此问题，似乎类似-检查sd卡是否可写将文本文件写入SD卡失败

Answer 2

if you run this application in android emulator you have to prepare sdcard through DevTools Terminal Emulator and check sdcard directory using linux command as $ls and allow to sdcard if not available prepare it and try the following

File file = new File(root, "/sdcard/agora.txt");
FileWriter fwriter = new FileWriter(file);
BufferedWriter out = new BufferedWriter(fwriter);
out.write("Hello world");
out.close();

//Use this in manifest.xml  
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Answer 3

您是否已在AndroidManifest.xml中对sdcard授予写权限？

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