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="http://www.mamicode.com/点击Android被调用" onclick="window.Android.showToast()" />