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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

1 package com.example.androidsdcard;  2   3 import android.content.Context;  4 import android.test.AndroidTestCase;  5 import android.util.Log;  6   7 public class MyTest extends AndroidTestCase {  8     private final String TAG="MyTest";  9     public MyTest(){ 10          11     } 12     public void saveFile(){//测试文件写入 13         Context context=getContext(); 14         FileStream fileStream=new FileStream(context); 15         boolean flag=fileStream.savaFile("hello.txt","你好吗？"); 16         Log.i(TAG,"--->"+flag); 17          18     } 19     public void readFile(){//测试文件内容读取 20         Context context=getContext(); 21         FileStream fileStream=new FileStream(context); 22         String filename="hello.txt"; 23         String flag=fileStream.readFile(filename); 24         Log.i(TAG,"--->"+flag); 25          26     } 27  28 }

正文到此结束