存储数据的方式

[android]代码库

1.SharedPreferences,存储方式(key,value)

存储:
          editor = getSharedPreferences("lock", MODE_WORLD_WRITEABLE).edit();   //MODE设定权限,只能这个程序访问,或者所有程序都可以访问
          editor.putString("1","key"); //(key,value)键值对
          editor.commit();

取数据:
           getSharedPreferences("lock", MODE_WORLD_READABLE).getString("1","")


可以通过Toast显示到屏幕上: 
Toast.makeText(MainActivity.this, getSharedPreferences("lock", MODE_WORLD_READABLE).getString("1",""), Toast.LENGTH_SHORT).show();


2.文件读取和保存
MainActivity.Java:

package com.example.savedatademo;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.util.Scanner;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

    private Button saveBtn = null;
    private Button readBtn = null;
    private EditText input = null;
    private final static String FILE_NAME = "xth.txt"; // 设置文件的名称

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

        input = (EditText) findViewById(R.id.input);
        saveBtn = (Button) findViewById(R.id.btn1);
        readBtn = (Button) findViewById(R.id.btn2);

        saveBtn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                String data = input.getText().toString();
                save(data);
                Toast.makeText(MainActivity.this, "保存数据成功！", Toast.LENGTH_SHORT)
                        .show();
            }
        });
        readBtn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                StringBuffer sb = read();
                Toast.makeText(MainActivity.this, "读取数据为：" + sb,
                        Toast.LENGTH_SHORT).show();
            }
        });
    }

    private StringBuffer read() {
        FileInputStream in = null;
        Scanner s = null;
        StringBuffer sb = new StringBuffer();
        try {
            in = super.openFileInput(FILE_NAME);
            s = new Scanner(in);
            while (s.hasNext()) {
                sb.append(s.next());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return sb;
    }

    private void save(String data) {
        FileOutputStream out = null;
        PrintStream ps = null;
        try {
            out = super.openFileOutput(FILE_NAME, Activity.MODE_APPEND);
            ps = new PrintStream(out);
            ps.println(data);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (out != null) {
                try {
                    out.close();
                    ps.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

}

activity_main.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.savedatademo.MainActivity" >

    <EditText
        android:id="@+id/input"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入" />

    <Button
        android:id="@+id/btn1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/input"
        android:text="保存数据" />

    <Button 
        android:id="@+id/btn2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/btn1"
        android:text="读取数据"/>
</RelativeLayout>


3.读写SD卡上的数据

3.1申请权限: 

<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

3.2读写文件的函数

// 文件写操作函数
    private void write(String content) {
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) { // 如果sdcard存在
            File file = new File(Environment.getExternalStorageDirectory()
                    .toString()
                    + File.separator
                    + DIR
                    + File.separator
                    + FILENAME); // 定义File类对象
            if (!file.getParentFile().exists()) { // 父文件夹不存在
                file.getParentFile().mkdirs(); // 创建文件夹
            }
            PrintStream out = null; // 打印流对象用于输出
            try {
                out = new PrintStream(new FileOutputStream(file, true)); // 追加文件
                out.println(content);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (out != null) {
                    out.close(); // 关闭打印流
                }
            }
        } else { // SDCard不存在，使用Toast提示用户
            Toast.makeText(this, "保存失败，SD卡不存在！", Toast.LENGTH_LONG).show();
        }
    }

    // 文件读操作函数
    private String read() {

        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) { // 如果sdcard存在
            File file = new File(Environment.getExternalStorageDirectory()
                    .toString()
                    + File.separator
                    + DIR
                    + File.separator
                    + FILENAME); // 定义File类对象
            if (!file.getParentFile().exists()) { // 父文件夹不存在
                file.getParentFile().mkdirs(); // 创建文件夹
            }
            Scanner scan = null; // 扫描输入
            StringBuilder sb = new StringBuilder();
            try {
                scan = new Scanner(new FileInputStream(file)); // 实例化Scanner
                while (scan.hasNext()) { // 循环读取
                    sb.append(scan.next() + "\n"); // 设置文本
                }
                return sb.toString();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (scan != null) {
                    scan.close(); // 关闭打印流
                }
            }
        } else { // SDCard不存在，使用Toast提示用户
            Toast.makeText(this, "读取失败，SD卡不存在！", Toast.LENGTH_LONG).show();
        }
        return null;
    }