保存数据到SD卡的封装

封装类：

package com.example.testsave.util;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import android.content.Context;
import android.os.Environment;
import android.util.Log;
import android.widget.Toast;

public class SaveUtil {

    /**
     * 
     * @param filename
     * @param content
     * @throws Exception
     */
    public static void saveToSDCard(String filename, String content)
            throws Exception {
        File file = new File(Environment.getExternalStorageDirectory(),
                filename);// 指定文件存储目录为SD卡，文件名
        FileOutputStream outStream = new FileOutputStream(file);// 输出文件流
        outStream.write(content.getBytes());
        outStream.close();

        //如果没有a.txt会自动创建  加入true 会每次都追加  不加的话 则直接是新的文件 把a.txt替换掉  
//        File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath(), "a.txt");  
//        FileOutputStream fos = new FileOutputStream(file, true);  
//        fos.write("这个是存储数据".getBytes());  
//        //这个地方并没有必要调用这个刷新方法 因为close也自带close 但是要养成好习惯  
//        fos.flush();  
//        fos.close();  
    }

    /**
     * 
     * @param context
     * @return  true 存在   false 不存在
     */
    public static boolean isExist(Context context) {
        boolean isExist = false;
        try {
            // 判断SDCard是否存在，并且可以读写
            if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
                Toast.makeText(context, "yes", 1).show();
                isExist = true;
            } else {
                Toast.makeText(context, "no", 1).show();
                isExist = false;
            }
        } catch (Exception e) {
            Toast.makeText(context, "no", 1).show();
            e.printStackTrace();
        }
        return isExist;
    }

    /**
     * 
     * @param file
     * @throws Exception
     */
    public static void getToSDDate(String fileName) throws Exception{
        File file = new File(Environment.getExternalStorageDirectory(),
                fileName);
        FileInputStream fis = new FileInputStream(file);  
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(fis));  
        String s = bufferedReader.readLine();  
        //这个地方会显示这个是存储数据  
        Log.e("MainActivity", s);
        fis.close();  
    }
}

调用：

package com.example.testsave;

import com.example.testsave.util.SaveUtil;
import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity {

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

        boolean exist = SaveUtil.isExist(getApplicationContext());
        if (exist) {
            try {
                SaveUtil.saveToSDCard("1.txt", "test");  // 保存数据
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        try {
            SaveUtil.getToSDDate("1.txt");   // 根据名称获取保存的数据
        } catch (Exception e) {
            e.printStackTrace();
        }

//        Log.e("MainActivity", localUrl);
    }
}

网络下载文件的保存：
http://blog.youkuaiyun.com/pengyu1801/article/details/50085909

http://blog.youkuaiyun.com/pengyu1801/article/details/50085761