Android 内存读写 库,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:

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" >

android:id="@+id/input"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="请输入" />

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" />

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"/>

3.读写SD卡上的数据

3.1申请权限:

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;

}