android 开发-数据存储之文件存储

　　android的文件存储是通过android的文件系统对数据进行临时的保存操作，并不是持久化数据，例如网络上下载某些图片、音频、视频文件等。如缓存文件将会在清理应用缓存的时候被清除，或者是应用卸载的时候缓存文件或内部文件将会被清除。

　　以下是开发学习中所写的示例代码，以供日后查阅:

　　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=".MainActivity" >

     <EditText
         android:id="@+id/editText1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentTop="true"
         android:layout_marginTop="44dp"
         android:ems="10" />

     <Button
         android:id="@+id/button1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignRight="@+id/editText1"
         android:layout_below="@+id/editText1"
         android:layout_marginRight="57dp"
         android:layout_marginTop="23dp"
         android:text="保存信息" />

 </RelativeLayout>

activity_main.xml

　　activity:

 package com.example.android_data_storage_internal;

 import java.io.ByteArrayOutputStream;
 import java.io.InputStream;
 import java.net.URI;

 import org.apache.http.HttpResponse;
 import org.apache.http.client.HttpClient;
 import org.apache.http.client.methods.HttpGet;
 import org.apache.http.impl.client.DefaultHttpClient;

 import android.app.Activity;
 import android.content.Context;
 import android.os.AsyncTask;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.View;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.Toast;

 import com.example.android_data_storage_internal.file.FileService;
 /**
  * @author xiaowu
  * @note 数据存储之文件内容存储
  */
 /**
  * @author xiaowu
  * @note 数据存储之文件内容存储（内部文件存储包括默认的文件存储、缓存文件存储）
  *         通过context对象获取文件路径
  *             context.getCacheDir();
  *             context.getFilesDir();
  *         //操作文件的模式：如果需要多种操作模式，可对文件模式进行相加
         //int  MODE_PRIVATE 私有模式
         //int  MODE_APPEND 追加模式
         //int  MODE_WORLD_READABLE 可读
         //int  MODE_WORLD_WRITEABLE 可写
  */
 public class MainActivity extends Activity {
     private EditText editText ;
     private Button button ;
     private FileService fileService;
     private final String IMAGEPATH ="http://b.hiphotos.baidu.com/zhidao/pic/item/738b4710b912c8fcda0b7362fc039245d78821a0.jpg";
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         fileService = new FileService(this);
         button = (Button) findViewById(R.id.button1);
         editText = (EditText) findViewById(R.id.editText1);
         //增加按钮点击监听事件
         button.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
                 String info = editText.getText().toString().trim();
                 boolean flag = fileService.SaveContentToFile("info.txt", Context.MODE_APPEND, info.getBytes());
                 if(flag){
                     Toast.makeText(MainActivity.this, "保存文件成功", 0).show();
                 }
                 //网络下载图片存储之本地
 //                MyTask task = new MyTask();
 //                task.execute(IMAGEPATH);
             }
         });
     }
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         // Inflate the menu; this adds items to the action bar if it is present.
         getMenuInflater().inflate(R.menu.main, menu);
         return true;
     }
     //自定义异步任务，用于图片下载
     public class MyTask extends AsyncTask<String,  Integer, byte[]>{
         @Override
         protected byte[] doInBackground(String... params) {
             HttpClient httpClient = new  DefaultHttpClient();
             HttpGet httpGet = new HttpGet(params[0]);
             InputStream inputStream = null ;
             byte[] result = null;
             ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
             try {
                 //执行连接从response中读取数据
                 HttpResponse response = httpClient.execute(httpGet);
                 int leng = 0 ;
                 byte [] data = new byte[1024]  ;
                 if (response.getStatusLine().getStatusCode() == 200) {
                     inputStream = response.getEntity().getContent();
                     while((leng = inputStream.read(data)) != 0) {
                         byteArrayOutputStream.write(data, 0, leng);
                     }
                 }
                 result = byteArrayOutputStream.toByteArray();
                 fileService.SaveContentToFile("info.txt", Context.MODE_APPEND, result);
             } catch (Exception e) {
                 e.printStackTrace();
             }finally{
                 //关连接
                 httpClient.getConnectionManager().shutdown();
             }
             return result;
         }
     }
 }

　　文件读写工具类Utils

　　

 package com.example.android_data_storage_internal.file;

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

 import android.content.Context;

 /**
  * @author xiaowu
  * @NOTE android文件读写帮助类
  */
 public class FileService {
     private Context context;

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

     // fileName：文件名 mode:文件操作权限
     /**
      * @param fileName
      *            文件名
      * @param mode
      *            文件操作权限
      * @param data
      *            输出流读取的字节数组
      * @return
      */
     public boolean SaveContentToFile(String fileName, int mode, byte[] data) {
         boolean flag = false;
         FileOutputStream fileOutputStream = null;
         try {
             //通过文件名以及操作模式获取文件输出流
             fileOutputStream = context.openFileOutput(fileName, mode);
             fileOutputStream.write(data, 0, data.length);
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             if (fileOutputStream != null) {
                 try {
                     fileOutputStream.close();
                 } catch (Exception e) {
                     e.printStackTrace();
                 }
             }
         }
         return flag;
     }

     /**
      * @param fileName
      *            文件名称
      * @return 文件内容
      */
     public String readContentFromFile(String fileName) {
         byte[] result = null;
         FileInputStream fileInputStream = null;
         ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
         try {
             fileInputStream = context.openFileInput(fileName);
             int len = 0;
             byte[] data = new byte[1024];
             while ((len = fileInputStream.read(data)) != -1) {
                 outputStream.write(data, 0, len);
             }
             result = outputStream.toByteArray();
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             try {
                 outputStream.close();
             } catch (IOException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
         }
         return new String(result);
     }
     /**
      * @param fileName 文件名称
      * @param mode 文件权限
      * @param data  输出流读取的字节数组
      * @return 是否成功标识
      */
     public boolean saveCacheFile(String fileName, byte[] data) {
         boolean flag = false;
         //通过context对象获取文件目录
         File file = context.getCacheDir();
         FileOutputStream fileOutputStream = null;
         try {
             File foder = new File(file.getAbsolutePath()+"/txt");
             if( !foder.exists() ){
                 foder.mkdir();    //创建目录
             }
             fileOutputStream = new FileOutputStream(foder.getAbsolutePath()+"/"+fileName);
             fileOutputStream.write(data, 0, data.length);
 //                    context.openFileOutput("info.txt",
 //                    Context.MODE_PRIVATE);
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             try {
                 if (fileOutputStream != null) {
                     fileOutputStream.close();
                 }
             } catch (IOException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
         }
         System.out.println(file.getAbsolutePath());
         return flag;
     }
     /**
      * 获取android内存文件夹下的文件列表
      * @param path
      * @return
      */
     public File[] listFileDir(String path){
         //获取目录
         File file = context.getFilesDir();
 //        System.out.println("-->CacheDir"+context.getCacheDir());
 //        /data/data/com.example.android_data_storage_internal/cache
 //        System.out.println("-->FilesDir"+file);
 //        /data/data/com.example.android_data_storage_internal/files
         File root = new File(file.getAbsolutePath()+"/"+path);
         File[] listFiles = root.listFiles();
         return listFiles;
     }
 }

　　Junit单元测试类：

 package com.example.android_data_storage_internal;

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

 import com.example.android_data_storage_internal.file.FileService;
 /**
  * @author xiaowu
  * @note 单元测试类
  *
  */
 public class MyTest extends AndroidTestCase {
     private final String TAG = "MyTest";

     public void save() {
         FileService fileService = new FileService(getContext());
         //操作文件的模式：如果需要多种操作模式，可对文件模式进行相加
         //int  MODE_PRIVATE 私有模式
         //int  MODE_APPEND 追加模式
         //int  MODE_WORLD_READABLE 可读
         //int  MODE_WORLD_WRITEABLE 可写
         boolean flag = fileService.SaveContentToFile("login.txt", Context.MODE_PRIVATE,
                 "你好".getBytes());
         Log.i(TAG, "-->"+flag);
     }
     public void read(){
         FileService fileService = new FileService(getContext());
         String msg = fileService.readContentFromFile("info.txt");
         Log.i(TAG, "--->"+msg);
     }
     public void test(){
         FileService fileService = new FileService(getContext());
         fileService.saveCacheFile("my.txt","小五".getBytes());
     }
     public void test2(){
         FileService fileService = new FileService(getContext());
         fileService.listFileDir("my.txt");
     }
 }

　　清单文件：

　　

 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.example.android_data_storage_internal"
     android:versionCode="1"
     android:versionName="1.0" >

     <uses-sdk
         android:minSdkVersion="8"
         android:targetSdkVersion="18" />

     <instrumentation
         android:name="android.test.InstrumentationTestRunner"
         android:targetPackage="com.example.android_data_storage_internal" >
     </instrumentation>
     <!-- 增加用户访问网络权限 -->
     <uses-permission android:name="android.permission.INTERNET"/>

     <application
         android:allowBackup="true"
         android:icon="@drawable/ic_launcher"
         android:label="@string/app_name"
         android:theme="@style/AppTheme" >
         <!-- 引入用与Junit测试包 -->
         <uses-library android:name="android.test.runner" android:required="true"/>
         <activity
             android:name="com.example.android_data_storage_internal.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>

 </manifest>