為網絡視圖(WebView)補充一點導航的功能

上一篇"一個簡單的瀏覽器, 網絡視圖(WebView)"實在太簡單了, 現在為它補充一點導航的功能; 包括輸入網址, 前進，後退，重載, 當然還有退出.





按MENU按鈕可以調用菜單, 包括Goto, Forward，Back，Reload, Exit五個選項.

Goto(輸入網址): 屏幕上方會出現一個EditText和一個Button, 以輸入網址. 這是通過setVisibility()的方法做到需要時才顯示, 不需要時不顯示的效果. 按下GO按鈕, 應用程序會調用WebView.loadUrl()加載網址.

Exit(退出): 就是退出.

Forward(前進)/Back(後退): 在onPrepareOptionsMenu()中根據WebView.canGoForward()和WebView.CanGoBack()決定按鈕有沒有效, 再通過setEnabled()設定. 當被選擇時調用WebView.goForward()或WebView.goBack()實現.

Reload(重載): 調用WebView.loadUrl()重載網址.

首先，創建一個新/res/menu/的menu.xml文件
(可參考"使用XML定義Options Menu(選項菜單)")

<?xml version="1.0" encoding="UTF-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:id="@+id/gotourl"
        android:title="Goto" />
  <item android:id="@+id/exit"
        android:title="Exit" />
  <item android:id="@+id/goback"
        android:title="Back" />
  <item android:id="@+id/reload"
        android:title="Reload" />
  <item android:id="@+id/goforward"
        android:title="Forward" />
</menu>

修改main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<RelativeLayout
android:id="@+id/UrlEntry"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:shrinkColumns="0"
android:visibility="gone"
>
   <Button
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_alignParentRight="true"
       android:id="@+id/go"
       android:text="GO"
       />
   <EditText
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       android:layout_toLeftOf="@id/go"
       android:id="@+id/url"
       android:text="http://"
       />

</RelativeLayout>
<WebView android:id="@+id/mybrowser" 
   android:layout_width="fill_parent" 
   android:layout_height="fill_parent" 
   />
</LinearLayout>

修改源碼

package com.AndroidWebView;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RelativeLayout;

public class AndroidWebView extends Activity {
 
 WebView myBrowser;
 RelativeLayout myUrlEntry;
 EditText myUrl;
 Button myGoButton;
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        String myURL = "http://www.google.com/m/";       
        myBrowser=(WebView)findViewById(R.id.mybrowser);
        myUrlEntry = (RelativeLayout)findViewById(R.id.UrlEntry);
        myUrl = (EditText)findViewById(R.id.url);
        myGoButton = (Button)findViewById(R.id.go);
        myGoButton.setOnClickListener(myGoButtonOnClickListener);

        WebSettings websettings = myBrowser.getSettings();
        websettings.setSupportZoom(true);
        websettings.setBuiltInZoomControls(true); 
        websettings.setJavaScriptEnabled(true);

        myBrowser.setWebViewClient(new WebViewClient());

        myBrowser.loadUrl(myURL);
        
    }
    
    private Button.OnClickListener myGoButtonOnClickListener = new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   myBrowser.loadUrl(myUrl.getText().toString());
   myUrlEntry.setVisibility(View.GONE);
  }
     
    };

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
  // TODO Auto-generated method stub
  MenuInflater menuInflater = getMenuInflater();
  menuInflater.inflate(R.menu.menu, menu);
  return true;
 }
 
 @Override
 public boolean onPrepareOptionsMenu(Menu menu) {
  // TODO Auto-generated method stub
  if(myBrowser.canGoForward())
   menu.findItem(R.id.goforward).setEnabled(true);
  else
   menu.findItem(R.id.goforward).setEnabled(false);
  
  if(myBrowser.canGoBack())
   menu.findItem(R.id.goback).setEnabled(true);
  else
   menu.findItem(R.id.goback).setEnabled(false);
  
  myUrlEntry.setVisibility(View.GONE);
  
  return true;
 }

 @Override
 public boolean onOptionsItemSelected(MenuItem item) {
  // TODO Auto-generated method stub
  switch(item.getItemId()){
  case (R.id.exit):
   openExitDialog();
   break;
  case (R.id.gotourl):
   myUrlEntry.setVisibility(View.VISIBLE);
   break;
  case (R.id.goback):
   myBrowser.goBack();
   break;
  case (R.id.reload):
   myBrowser.reload();
   break;
  case (R.id.goforward):
   myBrowser.goForward();
   break;
    }
    return true;
 }
    
 private void openExitDialog()
 {
  new AlertDialog.Builder(this)
   .setTitle("Exit")
   .setMessage("Exit the Browser?" )
   .setNegativeButton("NO",
     new DialogInterface.OnClickListener(){
    public void onClick(DialogInterface dialoginterface, int i)
    {}
   })
   .setPositiveButton("YES",
     new DialogInterface.OnClickListener()
      {
       public void onClick(DialogInterface dialoginterface, int i)
       { finish();
       }
      })
   .show();
  }
    
}

注意: 需參考上一篇"一個簡單的瀏覽器, 網絡視圖(WebView)", 修改清單文件(AndroidManifest.xml).