Android 文件操作

Android 文件操作

Android集成了Java.IO库，所有java中基于“流”的输入输出类也可以在这里运用。

这里也展示一个简答的小例子。

fileService.java

package com.file.save2sdcard;

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

/**
 * 文件操作服務類
 * @author QT
 *
 */

public class fileService {

    private Context context;

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

    public fileService() {

    }

    public static String readFileFromSdcard(String fileName) {
        String message = "";

        FileInputStream fileInputStream = null;
        // 字節數組輸出流，寫到内存中，不需要關閉
        ByteArrayOutputStream byteOutputStream = new ByteArrayOutputStream();
        //文件
        File file = new File(Environment.getExternalStorageDirectory(),
                fileName);

        try {
            //对于外置存储卡进行读写操作，首先要确定状态
            if (Environment.MEDIA_MOUNTED.equals(Environment
                    .getExternalStorageState())) {
                fileInputStream = new FileInputStream(file);
                int len = 0;
                //缓冲数组
                byte[] data = new byte[1024];
                while ((len = fileInputStream.read(data)) != -1) {
                    byteOutputStream.write(data, 0, len);
                }
                message = byteOutputStream.toString();
                //messge=new String(byteOutputStream.toByteArray());
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return message;
    }

    /**
     * 保存文件到sd卡
     * 
     * @param fileName
     *            文件名稱
     * @param content
     *            内容
     * @return 文件是否保存的標志
     */

    public static boolean writefileToSdcard(String fileName, String content) {
        boolean flag = false;
        FileOutputStream fileOutputStream = null;
        // 设置文件路径和文件名
        File file = new File(Environment.getExternalStorageDirectory(),
                fileName);

        // 如果外置存储卡处于可用状态
        if (Environment.MEDIA_MOUNTED.equals(Environment
                .getExternalStorageState())) {
            try {
                fileOutputStream = new FileOutputStream(file);
                fileOutputStream.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 (fileOutputStream != null) {
                    try {
                        fileOutputStream.close();
                        fileOutputStream = null;
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }

        }

        return flag;
    }

}

FileServiceText.java 测试类

package com.file.save2sdcard;

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

/**
 * 文件操作測試類
 * @author QT
 *
 */
public class FileServiceText extends AndroidTestCase {
    public static String TAG="FileServiceText";

    public FileServiceText() {
        // TODO Auto-generated constructor stub
    }

    public void TestSaveFile(){
        Context context=getContext();
        fileService files=new fileService(context);
        boolean flag=files.writefileToSdcard("hello.txt", "看不見你的笑，我怎麽睡的着");
        Log.i(TAG, "---->>"+flag);

    }

    public void TestReadFile(){
        Context context=getContext();
        fileService files=new fileService(context);
        String message=files.readFileFromSdcard("hello.txt");
        Log.i(TAG, "---->>"+message);
    }
}

AndroidManifest.xml 添加权限和单元测试支持

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.file.save2sdcard"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="15"
        android:targetSdkVersion="19" />

    <!-- 添加读取外置存储卡的权限 -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <!-- 添加andorid单元测试 -->
    <instrumentation
        android:name="android.test.InstrumentationTestRunner"
        android:targetPackage="com.file.save2sdcard" >
    </instrumentation>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

        <!-- 添加单元测试类库 -->
        <uses-library android:name="android.test.runner"  />

        <activity
            android:name="com.file.save2sdcard.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>

运行结果

向SDCard保存数据





从SDCard得到数据