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Android连接网络异常：android.os.NetworkOnMainThreadException
package com.ccl.getp_w_picpath;
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.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;
@Override
protected 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);
}
public void getImage(View view){
String path = et_path.getText().toString().trim();
if(TextUtils.isEmpty(path)){
Toast.makeText(this, "地址不能为空", 0).show();
return;
}
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
System.out.println("响应码是--"+conn.getResponseCode());
if(conn.getResponseCode()==200){
//获取服务器返回的流数据
InputStream in = conn.getInputStream();
//将返回的流数据解析成图片
Bitmap bitmap = BitmapFactory.decodeStream(in);
//显示图片
iv.setImageBitmap(bitmap);
in.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}Android模拟器版本4.1.2
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异常解释:在主线程中的网络异常
原因:Android2.3版本后不允许在主线程中直接请求网络获取数据
解决方法（两种）：
一：onCreate方法中加入如下代码（不推荐使用,有可能阻塞Android主线程)
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}二：使用Android 的handler机制，另外开启一个子线程请求网络获取数据(推荐使用)
package com.ccl.getp_w_picpath;
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.os.Handler;
import android.os.Message;
import android.text.TextUtils;
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;
private String path;
//使用Handler更新主线程（UI线程)
private Handler handler = new Handler(){
public void handleMessage(Message msg) {
Bitmap bitmap = (Bitmap) msg.obj;
iv.setImageBitmap(bitmap);
};
};
@Override
protected 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);
}
public void getImage(View view){
path = et_path.getText().toString().trim();
if(TextUtils.isEmpty(path)){
Toast.makeText(this, "地址不能为空", 0).show();
return;
}
new Thread(){
public void run(){
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
System.out.println("响应码是--"+conn.getResponseCode());
if(conn.getResponseCode()==200){
//获取服务器返回的流数据
InputStream in = conn.getInputStream();
//将返回的流数据解析成图片
Bitmap bitmap = BitmapFactory.decodeStream(in);
//使用handler传递消息
Message msg = Message.obtain();
msg.obj = bitmap;//传递的数据
handler.sendMessage(msg);
in.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}.start();
}
}注意两点：
Message对象的创建使用obtain方法可以达到对象重用的目的,节省内存开销。
Message对象可以使用msg.what = 传递消息的类型,handler可以根据传递的消息类型做不同处理，优化代码如下：
package com.ccl.getp_w_picpath;
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.os.Handler;
import android.os.Message;
import android.text.TextUtils;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;
public class MainActivity extends Activity {
protected static final int SUCCESS = 0;
protected static final int ERROR = 1;
protected static final int NETWORK_ERROR = 2;
private EditText et_path;
private ImageView iv;
private String path;
//使用Handler更新主线程（UI线程)
private Handler handler = new Handler(){
public void handleMessage(Message msg) {
switch (msg.what) {
case SUCCESS:
Bitmap bitmap = (Bitmap) msg.obj;
iv.setImageBitmap(bitmap);
break;
case ERROR:
Toast.makeText(MainActivity.this, "获取图片失败", 0).show();
break;
case NETWORK_ERROR:
Toast.makeText(MainActivity.this, "连接网络失败", 0).show();
break;
}
};
};
@Override
protected 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);
}
public void getImage(View view){
path = et_path.getText().toString().trim();
if(TextUtils.isEmpty(path)){
Toast.makeText(this, "地址不能为空", 0).show();
return;
}
new Thread(){
public void run(){
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
System.out.println("响应码是--"+conn.getResponseCode());
if(conn.getResponseCode()==200){
//获取服务器返回的流数据
InputStream in = conn.getInputStream();
//将返回的流数据解析成图片
Bitmap bitmap = BitmapFactory.decodeStream(in);
//使用handler传递消息
Message msg = Message.obtain();
msg.obj = bitmap;//传递的数据
msg.what = SUCCESS;//传递的消息类型,handler可根据消息类型做不同处理
handler.sendMessage(msg);
in.close();
}else{
Message msg = Message.obtain();
msg.what = ERROR;
handler.sendMessage(msg);
}
} catch (Exception e) {
Message msg = Message.obtain();
msg.what = NETWORK_ERROR;
handler.sendMessage(msg);
e.printStackTrace();
}
}
}.start();
}
}
网站标题：Android连接网络异常：android.os.NetworkOnMainThreadException
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