Android Studio

Question

点击按钮后想要获得百度首页的信息并显示在TextView中，项目运行后，点击按钮，TextView没变化

package com.hjy.usingasynctask;

import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

public class MainActivity extends AppCompatActivity {

    TextView text;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        text = (TextView) findViewById(R.id.textView2);
        findViewById(R.id.read).setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                ReadURL("http://www.baidu.com");
            }
        });
    }

    public void ReadURL(String url){
        new AsyncTask<String, Void, String>(){
            @Override
            protected String doInBackground(String... params) {//可线程的run方法相似
                try {
                    URL url = new URL(params[0]);
                    URLConnection connection = url.openConnection();
                    InputStream iStream = connection.getInputStream();
                    InputStreamReader isr = new InputStreamReader(iStream);
                    BufferedReader br = new BufferedReader(isr);
                    String line;
                    StringBuilder builder = new StringBuilder();
                    while((line = br.readLine()) != null){
                        builder.append(line);
                    }
                    br.close();
                    iStream.close();
                    return  builder.toString();
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return null;
            }

            @Override
            protected void onPostExecute(String result){
                text.setText(result);
                super.onPostExecute(result);
            }

            @Override
            protected void onPreExecute(){
                super.onPreExecute();
            }

            @Override
            protected void onProgressUpdate(Void... values){
                super.onProgressUpdate(values);
            }

        }.execute(url);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.hjy.usingasynctask.MainActivity">


    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="读网页信息"
        android:id="@+id/read" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="New Text"
            android:id="@+id/textView2" />
    </ScrollView>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.hjy.usingasynctask">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Answer 1

还是不行。 运行没显示什么错误，就是有警告 W/System.err: Caused by: android.system.GaiException: android_getaddrinfo failed: EAI_NODATA (No address associated with hostname)

Answer 2

你把控件文本设置放在super.onPostExecute(result)下面

Answer 3

真的是手机不能上网的原因啊

Answer 4

确认手机联网了吗，确认给权限了吗