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:

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>