010_02带缓存的图片查看器

　　第一次连接网络下载图片后，将在本机/data/data/...下保存图片；第二次打开应用程序点击“获取图片”将直接从本机缓存获取。

缓存图片保存位置如下：

 

MainActivity.java

  1 package com.example.day10_02getpicturebycache;
  2 
  3 import java.io.File;
  4 import java.io.FileOutputStream;
  5 import java.io.InputStream;
  6 import java.net.HttpURLConnection;
  7 import java.net.URL;
  8 
  9  
 10 
 11 import android.app.Activity;
 12 import android.graphics.Bitmap;
 13 import android.graphics.BitmapFactory;
 14 import android.os.Bundle;
 15 import android.os.Handler;
 16 import android.os.Message;
 17 import android.view.Menu;
 18 import android.view.MenuItem;
 19 import android.view.View;
 20 import android.widget.ImageView;
 21 import android.widget.Toast;
 22 
 23 public class MainActivity extends Activity {
 24     @Override
 25     protected void onCreate(Bundle savedInstanceState) {
 26         super.onCreate(savedInstanceState);
 27         setContentView(R.layout.activity_main);
 28     }
 29  
 30     final static int MSG_DOWNLOAD_OK =1; 
 31     final static int MSG_DOWNLOAD_ERROR =2; 
 32 
 33      Handler handler = new Handler(){
 34         @Override
 35         public void handleMessage(Message msg) {
 36             super.handleMessage(msg);
 37             //针对message进行处理
 38             switch (msg.what) {
 39             case MSG_DOWNLOAD_OK:
 40                 ImageView iv= (ImageView) findViewById(R.id.iv_pic);
 41                 iv.setImageBitmap((Bitmap)msg.obj);
 42                 break;
 43             case MSG_DOWNLOAD_ERROR:
 44                 Toast.makeText(MainActivity.this, "下载失败", 1).show();
 45                 break;    
 46             default:
 47                 break;
 48             }         
 49         }    
 50     };
 51 
 52     public void getpicture(View v){
 53         File file = new File(getCacheDir(), "zy.jpg");
 54         if(file.exists()) {
 55             Bitmap bm =new BitmapFactory().decodeFile(file.getAbsolutePath());
 56             ImageView iv= (ImageView) findViewById(R.id.iv_pic);
 57             iv.setImageBitmap(bm);
 58         } 
 59         else {
 60             //下面的整个代码是从网络url下载对应的数据
 61             Thread tread = new Thread(){
 62                 public void run() {
 63                         String path = "http://192.168.3.30:8080/tomcat.gif";
 64                         try {
 65                             URL url = new URL(path);
 66                             HttpURLConnection  conn = (HttpURLConnection) url.openConnection();
 67                             //set paramter 3
 68                             conn.setReadTimeout(5000);
 69                             conn.setRequestMethod("GET");
 70                             conn.setConnectTimeout(5000);
 71                             // pending;
 72                             conn.connect();
 73                             
 74                             if (conn.getResponseCode()==200) {
 75                               InputStream is = conn.getInputStream();
 76                               //如何放到缓存？
 77                               File file = new File(getCacheDir(), "zy.jpg");
 78                               FileOutputStream fos = new FileOutputStream(file);
 79                               byte[] b =new byte[1024];
 80                               int len=0;
 81                               while ((len=is.read(b))!=-1) {
 82                                 fos.write(b, 0, len);
 83                               }
 84                               is.close();
 85                               fos.close();
 86               
 87                               //从一个保存的cache文件中，去得到一个bitmap对象。
 88                               Bitmap bm = new BitmapFactory().decodeFile(file.getAbsolutePath());
 89 
 90                               Message msg = handler.obtainMessage(); 
 91                               msg.what = MSG_DOWNLOAD_OK;
 92                               msg.obj  = bm;
 93                               handler.sendMessage(msg);
 94                               
 95                             }
 96                             else {
 97                               Message msg = handler.obtainMessage(); 
 98                               msg.what =MSG_DOWNLOAD_ERROR;
 99                               handler.sendMessage(msg);
100                                 //Toast.makeText(this, "下载失败", 1).show();
101                             }    
102                         }catch (Exception e) {
103                             e.printStackTrace();
104                         }
105                 };
106             };
107             tread.start();            
108         }
109     }
110 }

 

activity_main.xml

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5     android:orientation="vertical" >
 6 
 7     <TextView
 8         android:layout_width="wrap_content"
 9         android:layout_height="wrap_content"
10         android:text="hello_world" />
11     <Button 
12          android:layout_width="wrap_content"
13         android:layout_height="wrap_content"
14         android:text="获取图片" 
15         android:onClick="getpicture"/>
16     <ImageView
17         android:id="@+id/iv_pic"
18          android:layout_width="wrap_content"
19         android:layout_height="wrap_content"
20          android:src="@drawable/ic_launcher"
21         ></ImageView>
22 </LinearLayout>

 

AndroidManifest.xml中权限设置：

1     <uses-permission android:name="android.permission.INTERNET"/>

 

posted @ 2015-05-20 11:05  woodrow_woo  阅读(367)  评论(0)  编辑  收藏  举报