子线程
子线程通知主线程更新UI
AndroidManifest.xml文件：
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android_enjoy_thread"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/title_activity_main" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
xml文件：
<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" > <ScrollView android:id="@+id/scroll" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_weight="1" > <TextView android:id="@+id/textview" android:layout_width="fill_parent" android:layout_height="wrap_content" android:hint="@string/hello_world" /> </ScrollView> <EditText android:layout_marginLeft="10dip" android:id="@+id/edittext" android:layout_width="300dip" android:layout_height="wrap_content" android:hint="请输入网址http://：" /> <Button android:layout_marginLeft="105dip" android:id="@+id/button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="点击我"/> </LinearLayout>
java文件：
1.无子线程，无Handler处理器：
java代码：
import java.io.BufferedReader; import java.io.ByteArrayOutputStream; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.URL; import android.app.Activity; import android.os.Bundle; import android.text.TextUtils; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends Activity implements OnClickListener { private Button btn; private EditText et ; private TextView tv; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn = (Button)findViewById(R.id.button); et = (EditText)findViewById(R.id.edittext); tv = (TextView)findViewById(R.id.textview); btn.setOnClickListener(this); } @Override public void onClick(View v) { String path = et.getText().toString(); switch (v.getId()) { case R.id.button: if (TextUtils.isEmpty(path)) { Toast.makeText(getApplicationContext(), "请输入网址", 1).show(); } try { URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET"); conn.setConnectTimeout(5000); int code = conn.getResponseCode(); if (code == 200) { InputStream input = conn.getInputStream(); String text = InputStreamTools(input); tv.setText(text); }else{ Toast.makeText(getApplicationContext(), "输入网站不存在", 1).show(); } } catch (Exception e) { e.printStackTrace(); } break; } } //自定义一个读取输入流的方法 public String InputStreamTools(InputStream input){ //创建BufferedReader对象 读取一行 BufferedReader br = new BufferedReader(new InputStreamReader(input)); //创建ByteArrayOutputStream对象 ByteArrayOutputStream out = new ByteArrayOutputStream(); String line = null ; try { //边读边写，将内容写到ByteArrayOutputStream对象out中 while((line = br.readLine())!=null){ out.write(line.getBytes()); } } catch (Exception e) { e.printStackTrace(); } //将流转化为String类型，返回String类型 return out.toString(); } }
2.有子线程，无Handler处理器： java代码：
import java.io.BufferedReader; import java.io.ByteArrayOutputStream; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.URL; import android.app.Activity; import android.os.Bundle; import android.text.TextUtils; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; public class MainActivity extends Activity implements OnClickListener { protected static final int PATH_NULL = 1; protected static final int PATH_EXIST = 2; protected static final int PATH_ERROR = 3; private Button btn; private EditText et ; private TextView tv; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn = (Button)findViewById(R.id.button); et = (EditText)findViewById(R.id.edittext); tv = (TextView)findViewById(R.id.textview); btn.setOnClickListener(this); } @Override public void onClick(View v) { switch (v.getId()) { case R.id.button: new Thread(new Runnable() { String path = et.getText().toString(); @Override public void run() { if (TextUtils.isEmpty(path)) { System.out.println("请输入网址"); } try { URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET");//设置联网方式为GET方式 conn.setConnectTimeout(5000);//设置网络连接时间 int code = conn.getResponseCode(); if (code == 200) {//如果code的值为200，则表示联网成功，path有效 InputStream input = conn.getInputStream(); String text = InputStreamTools(input); System.out.println("网站内容："+text); }else { System.out.println("输入网址错误！"); } } catch (Exception e) { } } }).start(); break; } } //自定义一个读取输入流的方法 public String InputStreamTools(InputStream input){ //创建BufferedReader对象 读取一行 BufferedReader br = new BufferedReader(new InputStreamReader(input)); //创建ByteArrayOutputStream对象 ByteArrayOutputStream out = new ByteArrayOutputStream(); String line = null ; try { //边读边写，将内容写到ByteArrayOutputStream对象out中 while((line = br.readLine())!=null){ out.write(line.getBytes()); } } catch (Exception e) { e.printStackTrace(); } //将流转化为String类型，返回String类型 return out.toString(); } }
3.有子线程，有Handler处理器：
java代码：
import java.io.BufferedReader; import java.io.ByteArrayOutputStream; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.URL; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.text.TextUtils; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends Activity implements OnClickListener { protected static final int PATH_NULL = 1; protected static final int PATH_EXIST = 2; protected static final int PATH_ERROR = 3; private Button btn; private EditText et ; private TextView tv; private Handler handler = new Handler(){ /* (non-Javadoc) * @see android.os.Handler#handleMessage(android.os.Message) */ @Override public void handleMessage(Message msg) { switch (msg.what) { case PATH_NULL: Toast.makeText(getApplicationContext(), "请输入网址", 1).show(); break; case PATH_EXIST: String text = (String) msg.obj; tv.setText(text); break; case PATH_ERROR: Toast.makeText(getApplicationContext(), "输入网站不存在", 1).show(); break; default: break; } super.handleMessage(msg); } }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn = (Button)findViewById(R.id.button); et = (EditText)findViewById(R.id.edittext); tv = (TextView)findViewById(R.id.textview); btn.setOnClickListener(this); } @Override public void onClick(View v) { switch (v.getId()) { case R.id.button: new Thread(new Runnable() { String path = et.getText().toString(); @Override public void run() { if (TextUtils.isEmpty(path)) { Message msg = Message.obtain(); msg.what = PATH_NULL; handler.sendMessage(msg); } try { URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET");//设置联网方式为GET方式 conn.setConnectTimeout(5000);//设置网络连接时间 int code = conn.getResponseCode(); if (code == 200) {//如果code的值为200，则表示联网成功，path有效 InputStream input = conn.getInputStream(); String text = InputStreamTools(input); Message msg = Message.obtain(); msg.obj = text; msg.what = PATH_EXIST; handler.sendMessage(msg); }else { Message msg = Message.obtain(); msg.what = PATH_ERROR; handler.sendMessage(msg); } } catch (Exception e) { } } }).start(); break; } } //自定义一个读取输入流的方法 public String InputStreamTools(InputStream input){ //创建BufferedReader对象 读取一行 BufferedReader br = new BufferedReader(new InputStreamReader(input)); //创建ByteArrayOutputStream对象 ByteArrayOutputStream out = new ByteArrayOutputStream(); String line = null ; try { //边读边写，将内容写到ByteArrayOutputStream对象out中 while((line = br.readLine())!=null){ out.write(line.getBytes()); } } catch (Exception e) { e.printStackTrace(); } //将流转化为String类型，返回String类型 return out.toString(); } }
注意：1.AndroidManifest.xml中要配置访问网络的权限：<uses-permission android:name="android.permission.INTERNET"/>
2.为了避免线程争抢产生的安全隐患，google工程师在设计Android系统的时候，只有主线程才可以修改UI，子线程是不可以直接修改UI的，也不可以直接弹出Toast(土司)。
3.
