0911Android基础网络技术之WebView控件

WebView控件

　　应用于在自己的应用程序里嵌入一个浏览器。
　　下面通过例子来说明WebView的用法。

添加权限

    "android.permission.ACCESS_NETWORK_STATE"/>
    "android.permission.INTERNET"/>

在布局中添加WebView控件

"http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    android:gravity="center"
    tools:context=".MainActivity">

    "@+id/btn_connect_state"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="获取网络连接状态"/>
    "match_parent"
        android:layout_height="0dp"

        android:layout_weight="1">
        "@+id/webview"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            >
        "@+id/tv_error"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            />
        "@+id/progressBar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:visibility="invisible"
            style="?android:attr/progressBarStyleHorizontal"/>
    

主线程中设置WebView的一些属性

　　 首先初始化WebView对象

 mConnectivityManager= (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

　　WebView的getSetting()方法可以去设置一些浏览器的属性，这里调用了调用了setJavaScriptEnabled()方法来让WebView支持JavaScript脚本，另外还调用过了设置缩放等的方法

        // 设置可以支持缩放
        mWebView.getSettings().setSupportZoom(true);
// 设置出现缩放工具
        mWebView.getSettings().setBuiltInZoomControls(true);
//扩大比例的缩放
        mWebView.getSettings().setUseWideViewPort(true);
//自适应屏幕
        mWebView.getSettings().setLayoutAlgorithm(WebSettings.LayoutAlgorithm.SINGLE_COLUMN);
        mWebView.getSettings().setLoadWithOverviewMode(true);

　　通过调用WebView的laodUrL()方法来将网页显示在webView中，而不再打开一个浏览器。通过来NetworkInfo 返回网络连接的信息

  mWebView.loadUrl("http:/www.baidu.com");
    NetworkInfo info=mConnectivityManager.getActiveNetworkInfo();
                if(info!=null&&info.isConnected()){
                    Toast.makeText(getApplicationContext(),"有网络连接:  "+info.getTypeName(),Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(getApplicationContext(),"无网络连接",Toast.LENGTH_SHORT).show();
                }

　　通过设置按键监听器来设置按下手机返回按键时，如果打开了多级网页，则一级一级的往前退

//      按键监听，此处设置监听后退键
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode==KeyEvent.KEYCODE_BACK){
            if(mWebView.canGoBack()){
                mWebView.goBack();
                return true;
            }else{
                MainActivity.this.finish();
            }
        }
        return super.onKeyDown(keyCode, event);
    }

　　代码中调用了setWebChromeClient和setWebViewClient来设置进度条以及输入错误的页面，或者页面出错时返回的界面。

mWebView.setWebViewClient(new WebViewClient() {
            @Override
            public void onPageFinished(WebView view, String url) {
                super.onPageFinished(view, url);
                mProgressBar.setVisibility(View.INVISIBLE);
            }

            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                super.onPageStarted(view, url, favicon);
                mProgressBar.setVisibility(View.VISIBLE);
            }

            @Override
            public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
                super.onReceivedError(view, errorCode, description, failingUrl);
                mWebView.setVisibility(View.GONE);
                mTvError.setText("加载失败");
            }
        });

        mWebView.setWebChromeClient(new WebChromeClient(){
            @Override
            public void onProgressChanged(WebView view, int newProgress) {
                super.onProgressChanged(view, newProgress);
                mProgressBar.setProgress(newProgress);
            }
        });

　　主线程全部代码

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements View.OnClickListener{
    private TextView mTvError;
    private Button mBtnConncectState;
    private WebView mWebView;
    private ProgressBar mProgressBar;
    private ConnectivityManager mConnectivityManager;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mBtnConncectState= (Button) findViewById(R.id.btn_connect_state);
        mWebView= (WebView) findViewById(R.id.webview);
        mTvError= (TextView) findViewById(R.id.tv_error);
        mProgressBar= (ProgressBar) findViewById(R.id.progressBar);

        // 设置可以支持缩放
        mWebView.getSettings().setSupportZoom(true);
// 设置出现缩放工具
        mWebView.getSettings().setBuiltInZoomControls(true);
//扩大比例的缩放
        mWebView.getSettings().setUseWideViewPort(true);
//自适应屏幕
        mWebView.getSettings().setLayoutAlgorithm(WebSettings.LayoutAlgorithm.SINGLE_COLUMN);
        mWebView.getSettings().setLoadWithOverviewMode(true);

//         初始化 ConnectivityManager对象
        mConnectivityManager= (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

//        设置webview支持JavaScript脚本
        mWebView.getSettings().setJavaScriptEnabled(true);
//        webview
        mWebView.setWebViewClient(new WebViewClient() {
            @Override
            public void onPageFinished(WebView view, String url) {
                super.onPageFinished(view, url);
                mProgressBar.setVisibility(View.INVISIBLE);
            }

            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                super.onPageStarted(view, url, favicon);
                mProgressBar.setVisibility(View.VISIBLE);
            }

            @Override
            public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
                super.onReceivedError(view, errorCode, description, failingUrl);
                mWebView.setVisibility(View.GONE);
                mTvError.setText("加载失败");
            }
        });

        mWebView.setWebChromeClient(new WebChromeClient(){
            @Override
            public void onProgressChanged(WebView view, int newProgress) {
                super.onProgressChanged(view, newProgress);
                mProgressBar.setProgress(newProgress);
            }
        });

        mBtnConncectState.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch(v.getId()){
            case R.id.btn_connect_state:
//                打开百度,根据传入的参数再去加载新的网页
                mWebView.loadUrl("http:/www.baidu.com");
//                mWebView.loadUrl("http:/.fdsafsaidu.com");

                NetworkInfo info=mConnectivityManager.getActiveNetworkInfo();
                if(info!=null&&info.isConnected()){
                    Toast.makeText(getApplicationContext(),"有网络连接:  "+info.getTypeName(),Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(getApplicationContext(),"无网络连接",Toast.LENGTH_SHORT).show();
                }
                break;
            default:
                break;
        }
    }

//      按键监听，此处设置监听后退键
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode==KeyEvent.KEYCODE_BACK){
            if(mWebView.canGoBack()){
                mWebView.goBack();
                return true;
            }else{
                MainActivity.this.finish();
            }
        }
        return super.onKeyDown(keyCode, event);
    }
}

　　输入这个网址时http:/.fdsafsaidu.com（不存在的网址）
　　

　　输入百度