【数据存储】利用IO流操作文件

package org.lxh.demo;
import java.io.File; import java.io.FileOutputStream;
import java.io.PrintStream;  import android.app.Activity;
import android.os.Bundle;
public class FileOperate extends Activity {
    // 设置文件名称
    private static final String FILENAME =
                   "/mnt/sdcard/mldndata/mymldn.txt" ;    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        super.setContentView(R.layout.main);
        // 定义要操作的文件
        File file = new File(FILENAME) ;     
        // 文件不存在
        if(!file.getParentFile().exists()) {
            // 创建文件夹路径
            file.getParentFile().mkdirs() ;    
        }
        // 打印流对象用于输出
        PrintStream out = null;
        try {
            out = new PrintStream(new FileOutputStream(file));
            out.println("噜啦啦啦啦啦啦啦");
        } catch (Exception e) {
            e.printStackTrace() ;
        } finally {    // 一定要关闭流
            if(out != null) {
                out.close() ;
            }
        }
    }
}



<!-- 运行操作sdcard的权限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

从sdcard读取文件

File file2 = new File(FILENAME);
        if (!file2.getParentFile().exists()) {
            file2.getParentFile().mkdirs();
        }
        Scanner scann = null;
        try {
            scann = new Scanner(new FileInputStream(file2));
            while (scann.hasNext()) {
                this.tv_msg.append(scann.next() + "\n");
                
            }
        } catch (Exception e) {
            // TODO: handle exception
        } finally {
            if (scann != null) {
                scann.close();
            }
        }