Android开发学习---如何写数据到外部存储设备(sd卡),Environment.getExternalStorageDirectory,怎么获取sd卡的大小?

package com.amos.datasave;

import java.io.File;
import java.io.FileOutputStream;

import android.annotation.SuppressLint;
import android.content.Context;
import android.os.Environment;
import android.util.Log;
import android.widget.Toast;

@SuppressLint("WorldWriteableFiles")
public class savePasswordService {
    private Context context;

    private String tag = "savePasswordService";

    public savePasswordService(Context context) {
        this.context = context;
    }

    public void savePasswordToFile(String name, String password) {
        // 这里设置文件的权限
        String content = name + ":" + password;
        Log.d(tag, "设置文件的读写权限");
        try {
            FileOutputStream fileOutput = context.openFileOutput("LoginTestConfig.txt", Context.MODE_WORLD_READABLE | Context.MODE_WORLD_WRITEABLE);
            fileOutput.write(content.getBytes());
            fileOutput.flush();
            fileOutput.close();
        } catch (Exception e) {
            Log.d(tag, "设置文件的读写权限失败!");
            e.printStackTrace();
        }
    }
    //写数据到sdcard
    public void savePasswordToSDCard(String name, String password) {
        // android 2.1 /sdcard/xx.txt
        // android 2.2 /mnt/sdcard/xx.txt
        // self_define /excard/xx.txt
        
//        File externalStorageDirectory = Environment.getExternalStorageDirectory();
//        String path = externalStorageDirectory.getPath();
//        System.out.println("path:" + path);

        // 要存储的内容
        String content = name + ":" + password;
        
        Log.d(tag, "检验sdcard是否可用?");
        //判断sdcard是否存在?
        if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
            Log.d(tag, "sdcard不可用!");
            Toast.makeText(context, "没有找到SDCard!", Toast.LENGTH_LONG);
            return ;
        };
        
        try {
            // File file = new File("/sdcard/qqpassword.txt");
            // File file = new File(path + "/qqpassword2.txt");
            File file = new File(Environment.getExternalStorageDirectory(), "/qqpassword2.txt");
            FileOutputStream fos = new FileOutputStream(file);
            fos.write(content.getBytes());
            fos.flush();
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

}