SharedPreferences数据存储及内外部存储空间的读写方式

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一、简单案例

package com.administrator.cachedemo;  

import android.content.Context;  
import android.content.SharedPreferences;  
import android.support.v7.app.AppCompatActivity;  
import android.os.Bundle;  
import android.util.Log;  

public class MainActivity extends AppCompatActivity {  

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

    /** 
     * SharedPreferences存储数据 
     */  
    private void testSharedPreferences(){  
        /** 
         * 第一个参数：存放在私有空间里的文件名称 
         * Context.MODE_PRIVATE支持读和写 
         */  
        SharedPreferences sharedPreferences = getSharedPreferences("sharedpreferences",  
                Context.MODE_PRIVATE);  
        /** 
         * 存储 
         */  
        sharedPreferences.edit().putInt("test", 1).commit();  
//        sharedPreferences.edit().putInt("test", 1).putInt("test2", 2).commit();//        editor.apply();  
//        sharedPreferences.getString("name",null);//第二个参数是获取的时候，没有时，传null  
        /** 
         * 读取 
         */  
        int value = sharedPreferences.getInt("test", 0);  
        Log.e("lxn", "value:" + value);  

    }  
}  

二、读取内外部存储空间

MainAvtivity.java

package com.administrator.cachedemo;  

import android.os.Environment;  
import android.support.v7.app.AppCompatActivity;  
import android.os.Bundle;  
import android.text.TextUtils;  
import android.util.Log;  

import java.io.BufferedReader;  
import java.io.File;  
import java.io.FileReader;  
import java.io.FileWriter;  

public class MainActivity extends AppCompatActivity {  

    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
    }  
    /** 
     * 读写内部存储空间 
     */  
    private void testInternalStorage() {  
        File cacheDir = getCacheDir();  
        File parentDir = new File(cacheDir, "mycache");  
        if (!parentDir.exists()) {//判断文件夹是否存在  
            parentDir.mkdirs();//mkdir()创建单个目录，mkdirs()创建多个逐级目录  
        }  
        File file = new File(parentDir,"text.txt");  
        try {  
            FileReader fileReader = new FileReader(file);  
            BufferedReader bufferedReader = new BufferedReader(fileReader);  
            String line = null;  
            while ((line = bufferedReader.readLine()) != null) {  
                Log.e("lxn", "line:" + line);  
            }  
            bufferedReader.close();  
            fileReader.close();  
        } catch (Exception e) {  
            Log.e("lxn", "testInternalStorage", e);  
        }  
    }  
    /** 
     * 读写外部存储空间 
     */  
    private void testRxternalStorage(){  
        if(TextUtils.equals(Environment.getExternalStorageState(),Environment.MEDIA_MOUNTED)){//判断SD卡是否挂载上  
            return;  
        }  
        File cacheDir = Environment.getExternalStorageDirectory();//获取外部存储目录  
        File parentDir = new File(cacheDir, "mycache");  
        if (!parentDir.exists()) {  
            parentDir.mkdirs();  
        }  

        File file = new File(parentDir, "test.txt");  
        try {  
            FileWriter fileWriter = new FileWriter(file);  
            fileWriter.write("this is test2");  
            fileWriter.flush();  
            fileWriter.close();  
        } catch (Exception e) {  
            Log.e("lxn", "testInternalStorage", e);  
        }  

        try {  
            FileReader fileReader = new FileReader(file);  
            BufferedReader bufferedReader = new BufferedReader(fileReader);  
            String line = null;  
            while ((line = bufferedReader.readLine()) != null) {  
                Log.e("lxn", "line:" + line);  
            }  
            bufferedReader.close();  
            fileReader.close();  
        } catch (Exception e) {  
            Log.e("lxn", "testInternalStorage", e);  
        }  
    }  
}