基础学习总结（七）--子线程及Handler

使用子线程获取网络图片
1.采用httpUrlConnection直连方式获取图片
2.采用子线程方式获取

 <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" >

     <ImageView android:id="@+id/iv_icon"
         android:layout_width="fill_parent"
         android:layout_height="0dip"
         android:layout_weight="1" />

     <LinearLayout
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:orientation="horizontal" >

         <EditText android:id="@+id/et_url"
             android:layout_width="0dip"
             android:layout_height="wrap_content"
             android:layout_weight="1" />

         <Button android:id="@+id/btn_submit"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:textSize="20sp"
             android:text="Go" />

     </LinearLayout>
 </LinearLayout>

线性布局

 public class MainActivity extends Activity implements OnClickListener {
     private final int SUCESS = 0;
     private final int ERROR=-1;
     private EditText etUrl;
     private ImageView ivIcon;

     private Handler hand=new Handler(){
         /*
          * 接收信息
          * */
         @Override
         public void handleMessage(Message msg){
             super.handleMessage(msg);
             if(msg.what==SUCESS){//识别访问handle的程序集
                 ivIcon.setImageBitmap((Bitmap)msg.obj);//设置bitmap显示图片
             }else if(msg.what==ERROR){
                 Toast.makeText(MainActivity.this, "抓取异常", 0).show();
             }
         }
     };

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         ivIcon = (ImageView)findViewById(R.id.iv_icon);
         etUrl = (EditText)findViewById(R.id.et_url);

         findViewById(R.id.btn_submit).setOnClickListener(this);
     }

     @Override
     public void onClick(View v) {
         // TODO Auto-generated method stub
         final String url=etUrl.getText().toString();
         //Bitmap bitmap=getImageFormat(url);
         //ivIcon.setImageBitmap(bitmap);//设置image显示图片
         new Thread(new Runnable(){
             @Override
             public void run(){
                 Bitmap bitmap=getImageFormat(url);
                 if(bitmap!=null){
                 Message msg=new Message();
                 msg.what=SUCESS;//设置handle区别码
                 msg.obj=bitmap;//将二进制数据放入msg
                 hand.sendMessage(msg);
                 }else{
                     Message msg=new Message();
                     msg.what=ERROR;
                     hand.sendMessage(msg);
                 }
             }
         }).start();

     }

     /**
      * 根据url链接网络获取图片返回
      * */
     private Bitmap getImageFormat(String url){
         HttpURLConnection conn=null;
         try {
             URL mUrl=new URL(url);
             conn =(HttpURLConnection)mUrl.openConnection();
             //设置传值方式
             conn.setRequestMethod("GET");
             //设置链接超时时间
             conn.setConnectTimeout(10000);
             //设置等待时间
             conn.setReadTimeout(5000);

             conn.connect();
             int code=conn.getResponseCode();//获得服务器响应对象
             if(code==200){
                 //访问成功
                 InputStream is=conn.getInputStream();//获得服务器返回的二进制数据
                 Bitmap bitmap = BitmapFactory.decodeStream(is);//将二进制流转换为bitmap图片

                 return bitmap;
             }else{
                 Log.i("MainActivity","链接不正常了...");
             }

         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }finally{
             if(conn!=null){
                 conn.disconnect();
             }
         }

         return null;
     }

 }

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

在不使用子线程的方式下：等待超时后程序异常
addroid not responding（应用程序无响应）因子程序等待阻塞了主线程 ANR异常
异常：
CalledFrowWrongThreadException：Only the original thread that creaded a view hierarchy can touch its views
只有原始的线程(主线程或ui线程)才能修改view对象

handler处理过程

 public class MainActivity extends Activity {

     private EditText etUserName;
     private EditText etPassword;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         etUserName = (EditText) findViewById(R.id.et_username);
         etPassword = (EditText) findViewById(R.id.et_password);
     }

     public void doGet(View v) {
         final String userName = etUserName.getText().toString();
         final String password = etPassword.getText().toString();

         new Thread(
                 new Runnable() {

                     @Override
                     public void run() {
                         // 使用get方式抓去数据
                         final String state = NetUtils.loginOfGet(userName, password);

                         // 执行任务在主线程中
                         runOnUiThread(new Runnable() {
                             @Override
                             public void run() {
                                 // 就是在主线程中操作
                                 Toast.makeText(MainActivity.this, state, 0).show();
                             }
                         });
                     }
                 }).start();
     }

     public void doPost(View v) {
         final String userName = etUserName.getText().toString();
         final String password = etPassword.getText().toString();

         new Thread(new Runnable() {
             @Override
             public void run() {
                 final String state = NetUtils.loginOfPost(userName, password);
                 // 执行任务在主线程中
                 runOnUiThread(new Runnable() {
                     @Override
                     public void run() {
                         // 就是在主线程中操作
                         Toast.makeText(MainActivity.this, state, 0).show();
                     }
                 });
             }
         }).start();
     }
 }

 public class NetUtils {

     private static final String TAG = "NetUtils";

     /**
      * 使用post的方式登录
      * @param userName
      * @param password
      * @return
      */
     public static String loginOfPost(String userName, String password) {
         HttpURLConnection conn = null;
         try {
             URL url = new URL("http://10.0.2.2:8080/ServerItheima28/servlet/LoginServlet");

             conn = (HttpURLConnection) url.openConnection();

             conn.setRequestMethod("POST");
             conn.setConnectTimeout(10000); // 连接的超时时间
             conn.setReadTimeout(5000); // 读数据的超时时间
             conn.setDoOutput(true);    // 必须设置此方法, 允许输出
 //            conn.setRequestProperty("Content-Length", 234);        // 设置请求头消息, 可以设置多个

             // post请求的参数
             String data = "username=" + userName + "&password=" + password;

             // 获得一个输出流, 用于向服务器写数据, 默认情况下, 系统不允许向服务器输出内容
             OutputStream out = conn.getOutputStream();
             out.write(data.getBytes());
             out.flush();
             out.close();

             int responseCode = conn.getResponseCode();
             if(responseCode == 200) {
                 InputStream is = conn.getInputStream();
                 String state = getStringFromInputStream(is);
                 return state;
             } else {
                 Log.i(TAG, "访问失败: " + responseCode);
             }
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             if(conn != null) {
                 conn.disconnect();
             }
         }
         return null;
     }

     /**
      * 使用get的方式登录
      * @param userName
      * @param password
      * @return 登录的状态
      */
     public static String loginOfGet(String userName, String password) {
         HttpURLConnection conn = null;
         try {
             String data = "username=" + URLEncoder.encode(userName) + "&password=" + URLEncoder.encode(password);
             URL url = new URL("http://10.0.2.2:8080/ServerItheima28/servlet/LoginServlet?" + data);
             conn = (HttpURLConnection) url.openConnection();

             conn.setRequestMethod("GET");        // get或者post必须得全大写
             conn.setConnectTimeout(10000); // 连接的超时时间
             conn.setReadTimeout(5000); // 读数据的超时时间

             int responseCode = conn.getResponseCode();
             if(responseCode == 200) {
                 InputStream is = conn.getInputStream();
                 String state = getStringFromInputStream(is);
                 return state;
             } else {
                 Log.i(TAG, "访问失败: " + responseCode);
             }
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             if(conn != null) {
                 conn.disconnect();        // 关闭连接
             }
         }
         return null;
     }

     /**
      * 根据流返回一个字符串信息
      * @param is
      * @return
      * @throws IOException
      */
     private static String getStringFromInputStream(InputStream is) throws IOException {
         ByteArrayOutputStream baos = new ByteArrayOutputStream();
         byte[] buffer = new byte[1024];
         int len = -1;

         while((len = is.read(buffer)) != -1) {
             baos.write(buffer, 0, len);
         }
         is.close();

         String html = baos.toString();    // 把流中的数据转换成字符串, 采用的编码是: utf-8

 //        String html = new String(baos.toByteArray(), "GBK");

         baos.close();
         return html;
     }
 }