Android 数据库文件存取至储存卡的方法

    package com.example.yanlei.wifi; import android.os.Bundle; import android.os.Environment; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.Toast; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.PrintStream; import java.util.Scanner; public class MainActivity extends AppCompatActivity { private Button btnSave=null; private Button btnRead=null; private File file=null; private static final String FILENAME="data.txt"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btnSave=(Button)super.findViewById(R.id.save); btnRead=(Button)super.findViewById(R.id.read); btnSave.setOnClickListener(new OnClickListener(){ public void onClick(View v) { PrintStream ps=null; //判断外部存储卡是否存在 if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){ Toast.makeText(getApplicationContext(), "读取失败，SD存储卡不存在！", Toast.LENGTH_LONG).show(); return; } //初始化File String path=Environment.getExternalStorageDirectory().toString() +File.separator +"genwoxue" +File.separator +FILENAME; file=new File(path); //如果当前文件的父文件夹不存在，则创建genwoxue文件夹 if(!file.getParentFile().exists()) file.getParentFile().mkdirs(); //写文件 try { ps = new PrintStream(new FileOutputStream(file)); ps.println("跟我学网址：www.genwoxue.com"); ps.println(""); ps.println("电子邮件：hello@genwoxue.com"); } catch (FileNotFoundException e) { e.printStackTrace(); }finally{ ps.close(); } Toast.makeText(getApplicationContext(), "保存成功！", Toast.LENGTH_LONG).show(); } }); btnRead.setOnClickListener(new OnClickListener(){ public void onClick(View v) { StringBuffer info=new StringBuffer(); //判断外部存储卡是否存在 if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){ Toast.makeText(getApplicationContext(), "读取失败，SD存储卡不存在！", Toast.LENGTH_LONG).show(); return; } //初始化File String path=Environment.getExternalStorageDirectory().toString() +File.separator +"genwoxue" +File.separator +FILENAME; file=new File(path); if(!file.exists()){ Toast.makeText(getApplicationContext(), "文件不存在！", Toast.LENGTH_LONG).show(); return; } //读取文件内容 Scanner scan=null; try { scan=new Scanner(new FileInputStream(file)); while(scan.hasNext()){ info.append(scan.next()).append("☆☆☆\n"); } Toast.makeText(getApplicationContext(), info.toString(), Toast.LENGTH_LONG).show(); } catch (FileNotFoundException e) { e.printStackTrace(); }finally{ scan.close(); } } }); } }