// 检查SD卡是不插入和拔出

   public boolean isSdMounted(View view) {

      String staus = Environment.getExternalStorageState();

      if (Environment.MEDIA_MOUNTED.equals(staus)) {

         System.out.println("插入了SD卡");

         return true;

      } else if (Environment.MEDIA_UNMOUNTED.equals(staus)) {

         System.out.println("SD卡被拔出了");

         return false;

      }

      return false;

   }

   // 获取SD卡的路径

   public String getSdPath(View v) {

      File file = Environment.getExternalStorageDirectory();

      String path = file.getAbsolutePath();

      return path;

   }

   // 获取SD卡可用空间

   @SuppressLint("NewApi")

   public long getSdFreeSpace(View v) {

      File file = Environment.getExternalStorageDirectory();

      return file.getFreeSpace();

     // 格式化大小

   }

package com.example.qq;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.InputStreamReader;

import android.os.Bundle;

import android.app.Activity;

import android.text.TextUtils;

import android.view.Menu;

import android.view.View;

import android.widget.CheckBox;

import android.widget.EditText;

import android.widget.Toast;

public class MainActivity extends Activity {

	private EditText	etPwd;

	private EditText	etQQ;

	private CheckBox	cbRemPwd;

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.activity_main);

		etPwd = (EditText) findViewById(R.id.et_pwd);

		etQQ = (EditText) findViewById(R.id.et_qq);

		cbRemPwd = (CheckBox) findViewById(R.id.cb_rem_pwd);

		readData();

	}

	/**

	 * 从文件中读取数据显示在界面上

	 */

	private void readData() {

		File file = new File("/mnt/sdcard/waibu.txt");

		try {

			FileInputStream fis = new FileInputStream(file);

			BufferedReader br = new BufferedReader(new InputStreamReader(fis));

			String text = br.readLine();

			String[] content = text.split("==");

			String qq = content[0];

			String pwd = content[1];

			//把QQ号码和密码显示在文本输入框

			etQQ.setText(qq);

			etPwd.setText(pwd);

			br.close();

		} catch (Exception e) {

			e.printStackTrace();

		}

	}

	/**

	 * 1. 获取用户输入的QQ号码和密码

	 * 2. 做非空判断

	 * 3. 如果用户勾选了复选框，用文件存储密码

	 */

	public void gelogin(View v){

//		System.out.println("点击了按钮");

		String pwd = etPwd.getText().toString().trim();

		String qq = etQQ.getText().toString().trim();

		if(TextUtils.isEmpty(pwd) || TextUtils.isEmpty(qq)){

			Toast.makeText(this, "亲，请输入QQ号码或者密码哦  :) ", 0).show();

			return;

		}

		//判断用户是否勾选复选框

		boolean checked = cbRemPwd.isChecked();

		if (checked) {

			//用文件存储密码

			try {

				File file = new File("/mnt/sdcard/waibu.txt");

				FileOutputStream fos = new FileOutputStream(file);

				String text = qq+"=="+pwd;

				fos.write(text.getBytes());

				//释放资源

				fos.close();

				Toast.makeText(this, "密码存储成功，/mnt/sdcard/waibu.txt", 0).show();

			} catch (Exception e) {

				e.printStackTrace();

				Toast.makeText(this, "存储失败了  :( ", 0).show();

			}

		}

	}

}