# WebView

## 用處

把網頁直接嵌入 App 中。

## 範例

```java
package com.example.yi.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private WebView webview ;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getSupportActionBar().hide();
        setContentView(R.layout.activity_main);

        //webview use to call own site
        webview =(WebView)findViewById(R.id.webView);

        webview.setWebViewClient(new WebViewClient());
        webview.getSettings().setJavaScriptEnabled(true);
        webview.getSettings().setDomStorageEnabled(true);
        webview.loadUrl("https://www.google.com");
    }
}
```

在 /layout/activity\_main.xml 加入以下

```markup
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <WebView  xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/webView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        />
</android.support.constraint.ConstraintLayout>
```

最後記得在 `Android Manifest` 加上permission

```markup
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.yi.myapplication" >
    <application>
        .....
    </application>
    <uses-permission android:name="android.permission.INTERNET" />

</manifest>
```

如果要讓畫面符合螢幕寬度可以在 `MainActivity.java` 加上以下兩行

```javascript
webview.getSettings().setLoadWithOverviewMode(true);
webview.getSettings().setUseWideViewPort(true);
```

## 注意事項

用以前的方法隱藏 title bar 容易造成 crash，建議使用以下方法

> <https://stackoverflow.com/questions/23293586/app-crashing-when-trying-to-hide-the-title-bar?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa>

## 讓第三方Oauth可使用

因為通常會跳出另一個視窗讓使用者輸入帳號密碼，所以可使用如下

> <https://stackoverflow.com/a/19068076/4622645>

```java
package com.example.yi.myapplication;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.Uri;
import android.net.http.SslError;
import android.os.Build;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.webkit.CookieManager;
import android.webkit.SslErrorHandler;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.Toast;


public class MainActivity extends Activity {

    /* URL saved to be loaded after fb login */
    private static final String target_url="https://sakatu.com";
    private static final String target_url_prefix="www.sakatu.com";
    private Context mContext;
    private WebView mWebview;
    private WebView mWebviewPop;
    private FrameLayout mContainer;
    private long mLastBackPressTime = 0;
    private Toast mToast;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        CookieManager cookieManager = CookieManager.getInstance();
        cookieManager.setAcceptCookie(true);
      mWebview =(WebView)findViewById(R.id.webView);
       mContainer = (FrameLayout) findViewById(R.id.webview_frame);
        WebSettings webSettings = mWebview.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webSettings.setAppCacheEnabled(true);
        webSettings.setJavaScriptCanOpenWindowsAutomatically(true);
        webSettings.setSupportMultipleWindows(true);
        mWebview.setWebViewClient(new UriWebViewClient());
        mWebview.setWebChromeClient(new UriChromeClient());


        mWebview.setWebViewClient(new WebViewClient());
        mWebview.getSettings().setJavaScriptEnabled(true);
        mWebview.getSettings().setDomStorageEnabled(true);
        mWebview.loadUrl(target_url);

        mWebview.getSettings().setLoadWithOverviewMode(true);
        mWebview.getSettings().setUseWideViewPort(true);

        mContext=this.getApplicationContext();

    }


    private class UriWebViewClient extends WebViewClient {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            String host = Uri.parse(url).getHost();
            //Log.d("shouldOverrideUrlLoading", url);
            if (host.equals(target_url_prefix))
            {
                // This is my web site, so do not override; let my WebView load
                // the page
                if(mWebviewPop!=null)
                {
                    mWebviewPop.setVisibility(View.GONE);
                    mContainer.removeView(mWebviewPop);
                    mWebviewPop=null;
                }
                return false;
            }

            if(host.equals("m.facebook.com"))
            {
                return false;
            }
            // Otherwise, the link is not for a page on my site, so launch
            // another Activity that handles URLs
            Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
            startActivity(intent);
            return true;
        }

        @Override
        public void onReceivedSslError(WebView view, SslErrorHandler handler,
                                       SslError error) {
            Log.d("onReceivedSslError", "onReceivedSslError");
            //super.onReceivedSslError(view, handler, error);
        }
    }

    class UriChromeClient extends WebChromeClient {

        @Override
        public boolean onCreateWindow(WebView view, boolean isDialog,
                                      boolean isUserGesture, Message resultMsg) {
            mWebviewPop = new WebView(mContext);
            mWebviewPop.setVerticalScrollBarEnabled(false);
            mWebviewPop.setHorizontalScrollBarEnabled(false);
            mWebviewPop.setWebViewClient(new UriWebViewClient());
            mWebviewPop.getSettings().setJavaScriptEnabled(true);
            mWebviewPop.setLayoutParams(new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                    ViewGroup.LayoutParams.MATCH_PARENT));
            mContainer.addView(mWebviewPop);
            WebView.WebViewTransport transport = (WebView.WebViewTransport) resultMsg.obj;
            transport.setWebView(mWebviewPop);
            resultMsg.sendToTarget();

            return true;
        }

        @Override
        public void onCloseWindow(WebView window) {
            Log.d("onCloseWindow", "called");
        }

    }
}
```

activity\_main.xml

```markup
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="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:background="#0099cc"
        tools:context=".MyActivity"
        android:id="@+id/webview_frame">

    <WebView  xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/webView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        />
</FrameLayout>
```

> 剛開始的時候有些網址不慣怎樣進入都是空白的，之後把code換成本章最上面那個，之後再換成這個就可以顯示了。


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