Android利用AsyncTask异步类实现网页内容放大缩小

本文实例为大家分享了asynctask异步类实现网页内容放大缩小的详细代码，供大家参考，具体内容如下

webactivity.java:

package com.supermario.filemanager;
import java.io.file;
import java.io.fileinputstream;
import java.io.filenotfoundexception;
import java.io.ioexception;
import org.apache.http.protocol.http;
import android.app.activity;
import android.app.alertdialog;
import android.content.dialoginterface;
import android.content.dialoginterface.onclicklistener;
import android.os.asynctask;
import android.os.bundle;
import android.view.view;
import android.webkit.websettings;
import android.webkit.webview;
import android.widget.relativelayout;
import android.widget.zoomcontrols;
public class webactivity extends activity {
 //网页浏览器
 private webview webview;
 //进度条布局和网页内容主体布局
 private relativelayout loadinglayout,weblayout;
 //放大缩小控制器
 private zoomcontrols zoomcontrols; 
 @override
 protected void oncreate(bundle savedinstancestate) {
 super.oncreate(savedinstancestate);
 setcontentview(r.layout.web);
 //初始化页面组件
 webview = (webview)findviewbyid(r.id.webkit);
 loadinglayout = (relativelayout)findviewbyid(r.id.loadinglayout);
 weblayout = (relativelayout)findviewbyid(r.id.weblayout);
 zoomcontrols = (zoomcontrols)findviewbyid(r.id.zoomcontrols); 
 websettings websettings = webview.getsettings();
 //设置可以使用js脚本
 websettings.setjavascriptenabled(true);
 //执行异步进程
 new myasynctask().execute(""); 
 }
 private void reading(){
 string filepath = getintent().getstringextra("filepath");
 if (filepath != null) {
  //读取文件
  webview.loaddata(readwebdatatostringfrompath(filepath, new filereadoverback() {
  @override
  public void filereadover() {
  }
  }), "text/html", http.utf_8);
 } else {
  new alertdialog.builder(webactivity.this).settitle("出错了").setmessage("获取文件路径出错!").setpositivebutton("返回", new onclicklistener() {
  @override
  public void onclick(dialoginterface dialog, int which) {
   webactivity.this.finish();
  }
  });
 }
 }
 //将网页数据读取到一个字符串变量中
 private string readwebdatatostringfrompath(string path,final filereadoverback filereadoverback){
 file file = new file(path);
 stringbuffer stringbuffer = new stringbuffer();
 try {
  //读取文件内容
  fileinputstream inputstream = new fileinputstream(file);
  byte[] bytes = new byte[1024];
  int readcount = 0;
  while ((readcount = inputstream.read(bytes)) > 0) {
  stringbuffer.append(new string(bytes, 0, readcount));
  }
  filereadoverback.filereadover();
 } catch (filenotfoundexception e) {
  return "文件不存在!";
 } catch (ioexception e) {
  return "文件读取错误!";
 }
 return stringbuffer.tostring();
 } 
 interface filereadoverback{
 void filereadover();
 }
 //异步处理类
 class myasynctask extends asynctask<string, string, string>{
 //首先执行的函数
 @override
 protected void onpreexecute() {
  super.onpreexecute();
  loadinglayout.setvisibility(view.visible);
  weblayout.setvisibility(view.gone);
 }
 //后台执行
 @override
 protected string doinbackground(string... params) {
  reading();
  return null;
 } 
 @override
 protected void onpostexecute(string result) {
  super.onpostexecute(result);
  //设置载入进度条隐藏
  loadinglayout.setvisibility(view.gone);
  //设置浏览器内容可见
  weblayout.setvisibility(view.visible);  
  // 放大按钮
  zoomcontrols.setonzoominclicklistener(new view.onclicklistener() {
  //将网页内容放大
  @override
  public void onclick(view v) {
   webview.zoomin();
  }
  });
  // 缩小按钮
  zoomcontrols.setonzoomoutclicklistener(new view.onclicklistener() { 
  //将网页内容缩小
  @override
  public void onclick(view v) {
   webview.zoomout();
  }
  });
 } 
 }
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。