package com.example.jsdemo;

import android.os.Bundle;

import android.support.v7.app.AppCompatActivity;

import android.webkit.WebSettings;

import android.webkit.WebView;

public class MainActivity extends AppCompatActivity {

    private WebView wView;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        wView = (WebView) findViewById(R.id.wView);

        wView.loadUrl("file:///android_asset/demo1.html");

        WebSettings webSettings = wView.getSettings();

        //①设置WebView允许调用js

        webSettings.setJavaScriptEnabled(true);

        webSettings.setDefaultTextEncodingName("UTF-8");

        //②设置支持js调用java

        wView.addJavascriptInterface(new AndroidAndJSInterface(),"Android"");

    }

 class AndroidAndJSInterface{

        @JavascriptInterface

        public void showToast(){

            Toast.makeText(MainActivity.this, "我被js调用了", Toast.LENGTH_SHORT).show();

        }

    }

}

<input type="button" value="点击Android被调用" onclick="window.Android.showToast()" />