編寫一個Android程序,使用AsyncTask實現獲取網頁的Html代碼,並且使用TextView顯示。
MainActivity.java代碼:
package com.example.administrator.chapter_listener;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
class MainActivity extends AppCompatActivity{
private TextView text;
private ProgressBar mProgressBar=null;
private Button btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text=(TextView)findViewById(R.id.textView);
btn=(Button)findViewById(R.id.button4);
//爲按鈕綁定事件響應方法
btn.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view){
try {
download();
}catch (Exception e){
e.printStackTrace();
}
}
});
}
//重寫該方法,爲界面的按鈕提供事件響應方法
public void download() throws MalformedURLException{
CodeTask task=new CodeTask();
task.execute(new URL("https://www.baidu.com/"));
}
class CodeTask extends AsyncTask<URL,Integer,String>{
//完成實際的下載任務
protected String doInBackground(URL... params){
StringBuilder sb=new StringBuilder();
try{
URLConnection conn=params[0].openConnection();
//打開conn連接對應的輸入流,並把它包裝成BufferedReader
BufferedReader br=new BufferedReader(new InputStreamReader(conn.getInputStream(),"utf-8"));
String line=null;
}catch (Exception e){
e.printStackTrace();
}
return null;
}
@Override
protected void onPreExecute(){
mProgressBar.setVisibility(View.VISIBLE);
}
protected void onPostExecute(String result){
mProgressBar.setVisibility(View.GONE);
text.setText(result);
}
}
}
activity_main.xml佈局文件:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/RelativeLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.administrator.chapter_listener.MainActivity">
<ImageView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="@+id/imageView1"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"/>
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleLarge"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"/>
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="神奇文本" />
<Button
android:id="@+id/button4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="開始操作"
android:layout_marginTop="52dp"
android:layout_below="@+id/progressBar1"
android:layout_alignLeft="@+id/progressBar1"
android:layout_alignStart="@+id/progressBar1" />
</RelativeLayout>