无法将文件写入SD卡

Question

我写这个是为了在SD卡中存储一个文件，但它不起作用。

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();
    }
}

这个问题是怎么引起的，我该如何解决？我认为一切都很好，我也在清单上写下了许可。

Answer 1

如果你在android模拟器中运行这个应用程序，你必须通过DevTools终端模拟器准备sdcard，并使用linux命令检查sdcard目录为$ls，并允许使用sdcard如果不可用，请准备并尝试以下

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 2

您是否在AndroidManifest.xml中授予了对SD卡的写入权限？

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