1 <RelativeLayout 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     tools:context=".MainActivity" >
 6
 7     <Button
 8         android:onClick="click"
 9         android:layout_width="wrap_content"
10         android:layout_height="wrap_content"
11         android:layout_centerHorizontal="true"
12         android:layout_centerVertical="true"
13         android:text="点我" />
14
15 </RelativeLayout>

package com.itheima.anr;import android.app.Activity;
import android.os.Bundle;
import android.view.View;public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}public void click(View view){try {System.out.println(Thread.currentThread().getName());Thread.sleep(6000);//当前线程。
            } catch (InterruptedException e) {e.printStackTrace();}}}

package com.itheima.netimageviewer;import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Base64;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;public class MainActivity extends Activity {private EditText et_path;private ImageView iv;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);et_path = (EditText) findViewById(R.id.et_path);iv = (ImageView) findViewById(R.id.iv);}/*** 点击查看网络上的图片* * @param view*/public void click(View view) {String path = et_path.getText().toString().trim();// http://www.baidu.com/aa.pngif (TextUtils.isEmpty(path)) {Toast.makeText(this, "图片路径不能为空", 0).show();return;}//把文件名编码之后+缓冲的路径变成file文件File file = new File(getCacheDir(), Base64.encodeToString(path.getBytes(), Base64.DEFAULT));if (file.exists() && file.length() > 0) {System.out.println("图片存在，拿缓存");Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());iv.setImageBitmap(bitmap);} else {System.out.println("图片不存在，获取数据生成缓存");// 通过http请求把图片获取下来。try {// 1.声明访问的路径， url 网络资源 http ftp rtspURL url = new URL(path);// 2.通过路径得到一个连接 http的连接HttpURLConnection conn = (HttpURLConnection) url.openConnection();// 3.判断服务器给我们返回的状态信息。// 200 成功 302 重定向 404资源没找到 5xx 服务器内部错误int code = conn.getResponseCode();if (code == 200) {//这个流是用来接收图片的InputStream is = conn.getInputStream();// png的图片//这个输出流是吧图片写入安卓系统的储存区的FileOutputStream fos = new FileOutputStream(file);//读写操作byte[] buffer = new byte[1024];int len = -1;while ((len = is.read(buffer)) != -1) {fos.write(buffer, 0, len);}is.close();fos.close();//通过图片工厂来获取文件路径， 然后变成图片传递给控件Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());iv.setImageBitmap(bitmap);} else {// 请求失败Toast.makeText(this, "请求失败", 0).show();}} catch (Exception e) {e.printStackTrace();Toast.makeText(this, "发生异常，请求失败", 0).show();}}}
}

<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"tools:context=".MainActivity" ><EditTextandroid:text="http://www.baidu.com/img/bd_logo1.png"android:id="@+id/et_path"android:layout_width="match_parent"android:layout_height="wrap_content"android:hint="请输入网络图片的路径" /><Buttonandroid:onClick="click"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="查看" /><ImageViewandroid:id="@+id/iv"android:layout_width="wrap_content"android:layout_height="wrap_content" /></LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.himi.webpicturewatch"android:versionCode="1"android:versionName="1.0" ><uses-permission android:name="android.permission.INTERNET"/><uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/><uses-sdkandroid:minSdkVersion="15"android:targetSdkVersion="17" /><applicationandroid:allowBackup="true"android:icon="@drawable/ic_launcher"android:label="@string/app_name"android:theme="@style/AppTheme" ><activityandroid:name=".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>