How to interact with js in Android development

This time I will show you how to interact with js in Android development. What are the precautions for interacting with js in Android development? The following is a practical case, let's take a look.

When we develop Android applications, we often need to deal with web pages. If we are making a takeaway app now, there will be a polling advertising space on the homepage of the app. When we click on one of them, it will jump. Go to a wap webpage. There may be promotional information for several restaurants on this webpage. After the user clicks on a restaurant, we hope that the wap page will pop up to display the details of the restaurant. At this time, we need to use js to call java code to achieve this. . Or, if we need to share in a wap page, we may also need to use js to call java code to perform the sharing operation. There are many scenarios like this. If we need to implement this function, we must understand the interaction method between java and js.

Use of WebView

If we want to display a web page in Android, we will basically use the WebView component. Its

basic use is also very simple. If we want To load the Baidu homepage, you can write it like this: First declare it in the layout file

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
    <WebView 
        android:id="@+id/web_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" /></RelativeLayout>

and then use it in the java file

WebView webView = (WebView) findViewById(R.id.web_view);
webView.loadUrl("http://www.baidu.com");

At the same time, WebView also allows us to modify some default settings. Modification, for example, if we want to enable support for

javascript and be able to zoom, we need to make the following settings:

// 启用javascriptwebView.getSettings().setJavaScriptEnabled(true);
webView.getSettings().setUseWideViewPort(true);//是否可以缩放webView.getSettings().setSupportZoom(true);
webView.getSettings().setBuiltInZoomControls(true);if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) { 
    getSettings().setDisplayZoomControls(false);
}

However, if we want to handle various notifications when the page loads , request events, or monitor the loading progress of the page, etc., you need to use two other classes: WebViewClient and WebChromeClient. Among them, WebViewClient is mainly used to listen for notifications or request events. The methods we may use in development are mainly the following:

onPageStarted

onPageFinished

onReceivedError

shouldOverrideUrlLoading

The WebChromeClient is used to handle javascript, website icons, website titles, loading progress, etc. When we use WeChat, if we open a webpage, we will see a green stripe on it.

Progress bar, this function is achieved by overriding the onProgressChanged method of WebChromeClient:

public class CustomWebClient extends WebChromeClient { 
    @Override public void onProgressChanged(WebView view, int newProgress) { 
        if (newProgress == 100) { 
            mProgressBar.setVisibility(GONE); 
        } else { 
            if (mProgressBar.getVisibility() == GONE) { 
                mProgressBar.setVisibility(VISIBLE); 
            } 
            mProgressBar.setProgress(newProgress);
        } 
        super.onProgressChanged(view, newProgress); 
    }
}

In addition, WebView also provides the function of running javascript directly. For example, we can A simple dialog box pops up:

webView.loadUrl("javascript:alert(\"提示信息！\");");

Of course, if we want to execute js, then two conditions must be met. The first is to enable javascript support in the settings, that is, setJavascriptEnabled(true) needs to be called. The second is to set up WebChromeClient, both of which are indispensable.

I believe you have mastered the methods after reading these cases. For more exciting information, please pay attention to other related articles on the php Chinese website!

Related reading:

Basic JavaScript Data Types
How to Remember Account and Password in JS Code

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