WebView的返回功能

import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.webkit.WebViewClient;

/**
 * Created by Administrator on 2015/1/4.
 */
public class WebViewTest extends Activity implements View.OnKeyListener {
    private WebView webView;
    private String url = "http://www.baidu.com/";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.webview);
        webView = (WebView) findViewById(R.id.webView);
        webView.setWebChromeClient(new chromeClient());
        webView.setWebViewClient(new webViewClient());
        webView.getSettings().setJavaScriptEnabled(true);
        webView.getSettings().setAllowFileAccess(true);
        webView.getSettings().setPluginsEnabled(true);
        webView.getSettings().setAllowFileAccess(true);


        webView.setOnKeyListener(this);
        webView.loadUrl(url);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_weview, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.menu_settings:
                finish();
                System.exit(0);
                break;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public boolean onKey(View v, int keyCode, KeyEvent event) {
        if (event.getAction() == KeyEvent.ACTION_DOWN) {
            if (keyCode == KeyEvent.KEYCODE_BACK && webView.canGoBack()) {  //表示按返回键 时的操作
                webView.goBack();   //后退
                return true;    //已处理
            }
        }
        return false;
    }

    class chromeClient extends WebChromeClient {
        @Override
        public void onProgressChanged(WebView view, int newProgress) {
            if (newProgress == 100) {
            }
            super.onProgressChanged(view, newProgress);

        }
    }

    class webViewClient extends WebViewClient {
        //重写shouldOverrideUrlLoading方法，使点击链接后不使用其他的浏览器打开。
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            view.loadUrl(url);
            //如果不需要其他对点击链接事件的处理返回true，否则返回false
            return true;
        }
    }
}