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();
 }
 });
}
}
}