Android sdcard实现图片存储 、联网下载

本文实例介绍了sdcard存储图片下载简单操作，分享给大家供大家参考，具体内容如下

步骤 -- 在配置清单添加完联网权限后

1、res/layout界面布局

<linearlayout 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:orientation="vertical" >



  <imageview

    android:id="@+id/imageview"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content" />

  

   <button

    android:id="@+id/bt_download"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:text="图片下载"

    android:onclick="image_download" />



</linearlayout>

2、有2个类一个操作sdcard的文件工具类(fileutil)另外一个mainactivity类

fileutil类

//操作sdcard的文件工具类

public class fileutil {



 private static final string cache_dir = environment.getexternalstoragedirectory() + "/my_caches/images";



 private static int comp_jpg = 0;

 private static int comp_png = 1;

//判断sdcard 是否挂载(是否有sdcard)

 public static boolean ismounted(){

 string state = environment.getexternalstoragestate();

 return state.equals(environment.media_mounted);

 }



 //获取sdcard文件 根路径的绝对路径

 public static string getsdcard(){

 return environment.getexternalstoragedirectory().getabsolutepath();

 }



 //获取文件名 

 public static string getfilename(string url){

 return url.substring(url.lastindexof('/') + 1);

 }



 //保存文件 方法1

 

 public static void sava1(string url,byte[] data){

 //判断是否有sdcard

 if(!ismounted()){

 return ; 

 }

 //有sdcard

 //判断是否有缓存文件夹

 file dir = new file(cache_dir);

 if(!dir.exists()){

 //不存在缓存文件夹 创建文件夹用来保存文件

 dir.mkdirs();

 }

 //把文件 数据存到sdcard

 file file = new file(dir,getfilename(url));

 try {

 fileoutputstream fos = new fileoutputstream(file);

 fos.write(data);

 

 fos.close();

 } catch (exception e) {

 e.printstacktrace();

 }

 }

 

 //保存文件 方法2

 public static void sava2(string url,bitmap bitmap,int format){

 //判断 是否有sdcard

 if(!ismounted()){

 return ;

 }

 file dir = new file(cache_dir);

 if(!dir.exists()){

 dir.mkdirs();

 }

 //把 文件数据 写到 sdcard

 file file = new file(dir,getfilename(url));

 try {

 fileoutputstream fos = new fileoutputstream(file);

 //把图片文件写入缓存

 bitmap.compress((format == comp_jpg?compressformat.jpeg:compressformat.png), 100, fos);

 

 fos.close();

 } catch (exception e) {

 e.printstacktrace();

 }

 

 }

 //读取图片

 public static bitmap readimage(string url){

 if(!ismounted()){

 return null;

 }

 file file = new file(cache_dir,getfilename(url));

 if(file.exists()){

 return bitmapfactory.decodefile(file.getabsolutepath());

 }

 return null;

 }

 

 //清空 缓存目录

 public void clearcaches(){

 file dir = new file(cache_dir);

 file[] file_datas = dir.listfiles();

 for(file file : file_datas){

 file.delete();

 }

 }

 

}

mainactivity类

public class mainactivity extends activity {



 private imageview imageview;

 

 private string url = "http://b.hiphotos.baidu.com/image/pic/item/d1160924ab18972bf5f68cc8e0cd7b899f510ae7.jpg";

 @override

 protected void oncreate(bundle savedinstancestate) {

 super.oncreate(savedinstancestate);

 setcontentview(r.layout.activity_main);

 

 this.imageview = (imageview) this.findviewbyid(r.id.imageview);

 //设置默认图片

 imageview.setimageresource(r.drawable.ic_launcher);

 

 }

 //图片下载 按钮 点击事件 监听

 public void image_download(view view){

 //判断本地是否有图片

 bitmap bitmap = fileutil.readimage(url);

 if(bitmap != null){

 imageview.setimagebitmap(bitmap);

 }else{

 //没有图片 就发送联网请求

 new myasynctask().execute(url);

 }

 }

 

 //联网工具类

 public class myasynctask extends asynctask<string, void, byte[]>{



 @override

 protected byte[] doinbackground(string... params) {

 

 httpget get = new httpget(params[0]);

 httpclient client = new defaulthttpclient();

 httpresponse response;

 try {

 response = client.execute(get);

 if(response.getstatusline().getstatuscode() == 200){

 byte[] data = entityutils.tobytearray(response.getentity());

 fileutil.sava1(params[0], data);

 return data;

 }

 }

 catch (exception e) {

 e.printstacktrace();

 }

 return null;

 }

 @override

 protected void onpostexecute(byte[] result) {

 super.onpostexecute(result);

 if(result != null){

 bitmap bitmap = bitmapfactory.decodebytearray(result, 0, result.length);

 imageview.setimagebitmap(bitmap);

 }

 }

 

 }

}

以上就是本文的全部内容，希望对大家学习android软件编程有所帮助。