FileService.java也就是操作sdcard的工具类：

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package com.example.data_storage_sdcard.file;
 
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.os.Environment;
 
/**
 * sdcard的存在于上下文无关
 *
 * @author piaodangdehun
 *
 */
public class FileService {
 
    /*
     * 存放在sdcard的根目录
     */
    public boolean saveFileToSdcardRoot(String fileName, byte[] data) {
        boolean flag = false;
        /*
         * 先判断sdcard的状态，是否存在
         */
        String state = Environment.getExternalStorageState();
        FileOutputStream outputStream = null;
        File rootFile = Environment.getExternalStorageDirectory(); // 获得sdcard的根路径
        /*
         * 表示sdcard挂载在手机上，并且可以读写
         */
        if (state.equals(Environment.MEDIA_MOUNTED)) {
            File file = new File(rootFile, fileName);
            try {
                outputStream = new FileOutputStream(file);
                try {
                    outputStream.write(data, 0, data.length);
                    flag = true;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } finally {
                if (outputStream != null) {
                    try {
                        outputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return flag;
    }
 
    /*
     * 存放在sdcard下自定义的目录
     */
    public boolean saveFileToSdcardDir(String fileName, byte[] data) {
        boolean flag = false;
        /*
         * 先判断sdcard的状态，是否存在
         */
        String state = Environment.getExternalStorageState();
        FileOutputStream outputStream = null;
        File rootFile = Environment.getExternalStorageDirectory(); // 获得sdcard的根路径
        /*
         * 表示sdcard挂载在手机上，并且可以读写
         */
        if (state.equals(Environment.MEDIA_MOUNTED)) {
            File file = new File(rootFile.getAbsoluteFile() + /txt);
            if (!file.exists()) {
                file.mkdirs();
            }
            try {
                outputStream = new FileOutputStream(new File(file, fileName));
                try {
                    outputStream.write(data, 0, data.length);
                    flag = true;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } finally {
                if (outputStream != null) {
                    try {
                        outputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return flag;
    }
 
    /*
     * 用于读取sdcard的数据
     */
    public String readContextFromSdcard(String fileName) {
 
        String state = Environment.getExternalStorageState();
        File rooFile = Environment.getExternalStorageDirectory(); // 获得sdcard的目录
 
        FileInputStream inputStream = null;// 用于度取数据的流
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); // 用于存放独处的数据
 
        if (state.equals(Environment.MEDIA_MOUNTED)) {
            File file = new File(rooFile.getAbsoluteFile() + /txt/);// 在sdcard目录下创建一个txt目录
            File file2 = new File(file, fileName);
            int len = 0;
            byte[] data = new byte[1024];
            if (file2.exists()) {
                try {
                    inputStream = new FileInputStream(file2);
                    try {
                        while ((len = inputStream.read(data)) != -1) {
                            outputStream.write(data, 0, data.length);
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    return new String(outputStream.toByteArray());
                } catch (FileNotFoundException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } finally {
                    if (outputStream != null) {
                        try {
                            outputStream.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }
        return null;
    }
 
    /**
     * 对文件进行分类的保存到固定的文件中去
     *
     * @param fileName
     * @param data
     */
    public void saveFileToSdcardBySuff(String fileName, byte[] data) {
        // File file = Environment.getExternalStoragePublicDirectory();
        // 保存文件的目录
        File file = null;
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) {
 
            /*
             * 将不同的文件放入到不同的类别中
             */
            if (fileName.endsWith(.mp3)) {
                file = Environment
                        .getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC);
            } else if (fileName.endsWith(.jpg) || fileName.endsWith(.png)
                    || fileName.endsWith(.gif)) {
                file = Environment
                        .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
            } else if (fileName.endsWith(.mp4) || fileName.endsWith(.avi)
                    || fileName.endsWith(.3gp)) {
                file = Environment
                        .getExternalStoragePublicDirectory(Environment.DIRECTORY_MOVIES);
            } else {
                file = Environment
                        .getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
            }
            FileOutputStream outputStream = null;
            try {
                outputStream = new FileOutputStream(new File(file, fileName));
                try {
                    outputStream.write(data, 0, data.length);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } finally {
                if (outputStream != null) {
                    try {
                        outputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
 
    /*
     * 删除一个文件
     */
    public boolean deleteFileFromSdcard(String folder, String fileName) {
        boolean flag = false;
        File file = Environment.getExternalStorageDirectory();
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) {
            File exitFile = new File(file.getAbsoluteFile() + / + folder);
            if (exitFile.exists()) {
                exitFile.delete();
            }
        }
        return flag;
    }
}

HttpUtils.java访问网络的

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package com.example.data_storage_sdcard.http;
 
import java.io.IOException;
 
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
 
public class HttpUtils {
    /*
     *
     */
    public static byte[] getImage(String path) {
        byte[] data = null;
        HttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(path);
        try {
            HttpResponse response = httpClient.execute(httpPost);
            if (response.getStatusLine().getStatusCode() == 200) {
                data = EntityUtils.toByteArray(response.getEntity());
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            httpClient.getConnectionManager().shutdown();
        }
 
        return data;
 
    }
}

ImageCache.java将文件放到cache中的：

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package com.example.data_storage_sdcard.img;
 
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
 
import android.os.Environment;
 
public class ImageCache {
 
    public static  String saveImageCache(String fileName, byte[] data) {
        File file = Environment.getExternalStorageDirectory(); // 根目录
        FileOutputStream outputStream = null;
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) {
            try {
                outputStream = new FileOutputStream(new File(file, fileName));
                outputStream.write(data, 0, data.length);
 
                return file.getAbsolutePath() + / + fileName;
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (outputStream != null) {
                    try {
                        outputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return null;
    }
}

MainActivity.java

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package com.example.data_storage_sdcard;
 
import android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
 
import com.example.data_storage_sdcard.http.HttpUtils;
import com.example.data_storage_sdcard.img.ImageCache;
 
public class MainActivity extends Activity {
    private Button button;
    private ImageView imageView;
    private ProgressDialog progressDialog;
 
    private String imageName;
 
    private final String pathString = http://www.baidu.com/img/bd_logo1.png;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = (Button) this.findViewById(R.id.button1);
        imageView = (ImageView) this.findViewById(R.id.imageView1);
 
        progressDialog = new ProgressDialog(this);
        progressDialog.setTitle(下载提示);
        progressDialog.setMessage(load...);
        button.setOnClickListener(new OnClickListener() {
 
            @Override
            public void onClick(View v) {
                new MyTask().execute(pathString);
            }
        });
    }
 
    class MyTask extends AsyncTask<string,> {
 
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            progressDialog.show();
        }
 
        @Override
        protected byte[] doInBackground(String... params) {
            String name = params[0];
            imageName = name
                    .substring(name.lastIndexOf(/) + 1, name.length());
            return HttpUtils.getImage(params[0]);
        }
 
        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
        }
 
        @Override
        protected void onPostExecute(byte[] result) {
            super.onPostExecute(result);
            if (result != null) {
                Bitmap bm = BitmapFactory.decodeByteArray(result, 0,
                        result.length);
                imageView.setImageBitmap(bm);
                ImageCache.saveImageCache(, result);
            } else {
                imageView.setImageResource(R.drawable.ic_launcher);
            }
            progressDialog.dismiss();
        }
    }
 
    @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;
    }
 
}
</string,>

测试类：

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package com.example.data_storage_sdcard;
 
import java.io.FileWriter;
 
import com.example.data_storage_sdcard.file.FileService;
 
import android.nfc.Tag;
import android.test.AndroidTestCase;
import android.util.Log;
 
public class MyTest extends AndroidTestCase {
 
    public void saveFileToSdcardTest() {
        FileService fileService = new FileService();
 
        fileService.saveFileToSdcardRoot(aa.txt,
                jkhdsfjkhdskjfhdsjf.getBytes());
    }
 
    public void saveFileToSdcardDir() {
        FileService fileService = new FileService();
 
        fileService.saveFileToSdcardRoot(aa.txt,
                jkhdsfjkhdskjfhdsjf.getBytes());
    }
 
    public void readContextFromSdcardTest() {
        FileService fileService = new FileService();
        String msg = fileService.readContextFromSdcard(aa.txt);
        System.err.println(--> + msg);
    }
 
    public void saveFileToSdcardBySuffTest() {
        FileService fileService = new FileService();
        fileService.saveFileToSdcardBySuff(aa.avi,
                asdfkajsgdhagsdfhdgsf.getBytes());
    }
 
    public void delFile() {
        FileService fileService = new FileService();
        boolean flag = fileService.deleteFileFromSdcard(txt, aa.txt);
    }
}

需要在请单位按中加入访问网络的权限、操作sdcard的权限、测试的权限

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<!--?xml version=1.0 encoding=utf-8?-->
<manifest android:versioncode="1" android:versionname="1.0" package="com.example.data_storage_sdcard" xmlns:android="http://schemas.android.com/apk/res/android">
 
    <uses-sdk android:minsdkversion="8" android:targetsdkversion="18">
 
    <instrumentation android:name="android.test.InstrumentationTestRunner" android:targetpackage="com.example.data_storage_sdcard">
    </instrumentation>
    <!-- 添加访问sdcard的权限 -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE">
    <!-- 添加访问网络的权限 -->
    <uses-permission android:name="android.permission.INTERNET">
 
     
        <uses-library android:name="android.test.runner">
 
         
            <intent-filter>
                 
 
                <category android:name="android.intent.category.LAUNCHER">
            </category></action></intent-filter>
        </activity>
 
        <uses-library>
        </uses-library>
    </uses-library></application>
 
</uses-permission></uses-permission></uses-sdk></manifest>
 

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