Android数据存储------1,文件存储

第一步，改写AndroidManifest.xml,给手机的Scard卡授权

<!--添加Scard卡读写授权 -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

然后加单元测试instrumentation

 <instrumentation
        android:name="android.test.InstrumentationTestRunner"
        android:targetPackage="com.example.androidsdcard" >
    </instrumentation>

并且在application下加 <uses-library android:name="android.test.runner"/>

 <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <uses-library android:name="android.test.runner"/>
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

第二步，编写文件读写的类FileStream

package com.example.androidsdcard;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import android.content.Context;
import android.os.Environment;

public class FileStream {
    private Context context;

    public FileStream(Context context) {
        this.context = context;
    }

    public FileStream() {

    }
    //读取sd卡的文件内容
    public String readFile(String filename){
        FileInputStream inputStream=null;
        //字符缓冲流
        ByteArrayOutputStream outputStream=new ByteArrayOutputStream();
　　　　　//                 通过Environment获得sd卡的路径
        File file=new File(Environment.getExternalStorageDirectory(),filename);
        //判断sdcard是否存在
        if(Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())){
            try {
                inputStream=new FileInputStream(file);
                int len=0;
　　　　　　　　　//创建字节数组
                byte[]data=new byte[2048];
　　　　　　　　　　//按字节数组的大小进行读取
                while((len=inputStream.read(data))!=-1){
                    outputStream.write(data, 0, len);    
                }
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }finally{
                if(inputStream!=null){
                    try {
                        inputStream.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        }
        return new String(outputStream.toByteArray());
        
    }

    public boolean savaFile(String filename, String content) {
        boolean flag = false;
        FileOutputStream outputStream = null;
        File file = new File(Environment.getExternalStorageDirectory(),
                filename);
        if (Environment.MEDIA_MOUNTED.equals(Environment
                .getExternalStorageState())) {
            try {
                outputStream = new FileOutputStream(file);
                outputStream.write(content.getBytes());
                flag = true;
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {
                if (outputStream != null) {
                    try {
                        outputStream.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }

        }

        return flag;
    }

}

第三部，编写测试类进行单元测试，进行文件的读写

package com.example.androidsdcard;

import android.content.Context;
import android.test.AndroidTestCase;
import android.util.Log;

public class MyTest extends AndroidTestCase {
    private final String TAG="MyTest";
    public MyTest(){
        
    }
    public void saveFile(){//测试文件写入
        Context context=getContext();
        FileStream fileStream=new FileStream(context);
        boolean flag=fileStream.savaFile("hello.txt","你好吗？");
        Log.i(TAG,"--->"+flag);
        
    }
    public void readFile(){//测试文件内容读取
        Context context=getContext();
        FileStream fileStream=new FileStream(context);
        String filename="hello.txt";
        String flag=fileStream.readFile(filename);
        Log.i(TAG,"--->"+flag);
        
    }

}