package com.lixu.writetosd;

 import java.io.File;

 import java.io.FileOutputStream;

 import java.io.IOException;

 import android.app.Activity;

 import android.os.Bundle;

 import android.os.Environment;

 import android.widget.Toast;

 public class MainActivity extends Activity {

     @Override

     protected void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         setContentView(R.layout.activity_main);

         // 判断SD卡是否装载成功，否则提示错误。

         boolean isMounted = Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED);

         if (isMounted) {

             writetoSDcard();

             Toast.makeText(this, "写入成功！", 0).show();

         } else {

             Toast.makeText(this, "SD卡未装载！", 0).show();

         }

     }

     public void writetoSDcard() {

         FileOutputStream fos = null;

         File path = Environment.getExternalStorageDirectory();

         File dir = new File(path.getAbsoluteFile(), "lixu");

         // 创建特定名字的文件夹 判断文件夹是否存在，不存在创建。

         if (!dir.exists())

             dir.mkdir();

         // 定义特定名字的文件

         File file = new File(dir.getAbsoluteFile(), "lixu.txt");

         String str = "看到这句话就写入成功了！";

         byte[] buffer = str.getBytes();

         try {

             // 创建文件

             file.createNewFile();

             fos = new FileOutputStream(file);

             // 先将字符串装入字节数组后一次写入fos流，这样相当于缓存入一个容器再写入，效率高。

             fos.write(buffer, 0, buffer.length);

             fos.flush();

         } catch (IOException e) {

             e.printStackTrace();

         } finally {

             if (fos != null) {

                 try {

                     fos.close();

                 } catch (IOException e) {

                     e.printStackTrace();

                 }

             }

         }

     }

 }