pabloko/AndroidJSInterfaceComplexTypes.java

## AndroidJSInterfaceComplexTypes.java
//How it works: all the script relies on a tiny javascript stub injected to webView's document that uses Proxy api and json serialicing stuff. Calls to our internal objects are proxified to a single method "__mm_handle_method", that using reflection find the target method and populate arguments exchanged in json, plus a custom interface for methods passed as argument.

package es.pabloko.webviewbridge;

import android.app.Activity;
import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.webkit.JavascriptInterface;
import android.webkit.WebView;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class MainActivity extends AppCompatActivity {
    private String JSINTERFACE="Android";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);
        //WebView webView = findViewById(R.id.web);
        WebView webView = new WebView(this);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.addJavascriptInterface(new JSInterface(this, webView, JSINTERFACE), JSINTERFACE+"_stub");
        String html = "<!DOCTYPE html><html><head><meta charset=\"utf-8\"><script>"
                + "var __mm_cb={};function __mm_guid(){function _(){return Math.floor(65536*(1+Math.random())).toString(16).substring(1)}return\"__mm_method_\"+_()+_()+\"-\"+_()+\"-\"+_()+\"-\"+_()+\"-\"+_()+_()+_()}function __mm_callback(){var _=Array.from(arguments),n=_.shift();__mm_cb[n]&&__mm_cb[n].apply(null,_)}var __mm_method_handler="+JSINTERFACE+"_stub.__mm_method_handler.bind("+JSINTERFACE+"_stub),"+JSINTERFACE+"=new Proxy("+JSINTERFACE+"_stub,{get:function(_,r){return function(){for(var _=0;_<arguments.length;_++)if(\"[object Function]\"==={}.toString.call(arguments[_])){var n=__mm_guid();\"\"!=arguments[_].name&&(n=\"__mm_method_\"+arguments[_].name),__mm_cb[n]=arguments[_],arguments[_]=n}var m=__mm_method_handler(r,JSON.stringify(arguments));return JSON.parse(m).value}}});"
                + "</script></head><body>Android WebView JavascriptInterface Test</body></html>";
        webView.loadData(html, "text/html", "UTF-8");
        WebView.setWebContentsDebuggingEnabled(true);
        setContentView(webView);
    }

    public class JSCallback {
        private Context caller;
        private WebView wb;
        private String guid;
        public JSCallback(Context caller, WebView wb, String guid) {
            this.caller = caller;
            this.wb=wb;
            this.guid=guid;
        }
        public void call(Object... o) {
            StringBuilder stringBuilder = new StringBuilder();
            stringBuilder.append("try{");
            String separator = "";
            if (guid.startsWith("__mm_method_")) {
                stringBuilder.append("__mm_callback");
                stringBuilder.append("(");
                stringBuilder.append("'" + guid + "'");
                separator = ",";
            } else {
                stringBuilder.append(guid);
                stringBuilder.append("(");
            }
            for (Object param : o) {
                stringBuilder.append(separator);
                separator = ",";
                if (param instanceof String) {
                    stringBuilder.append("'");
                    stringBuilder.append(((String) param).replace("'", "\'"));
                    stringBuilder.append("'");
                } else
                    stringBuilder.append(param);
            }
            stringBuilder.append(")}catch(error){console.error(error.message);}");
            final String call = stringBuilder.toString();
            ((Activity)caller).runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT) {
                        wb.evaluateJavascript(call, null);
                    } else {
                        wb.loadUrl("javascript:" + call);
                    }
                }
            });
        }
    }

    public class JSInterface {
        private Context caller;
        private WebView wb;
        private String jsinterfacename;

        public JSInterface(Context caller, WebView wb, String jsc) {
            this.wb = wb;
            this.jsinterfacename = jsc;
            this.caller = caller;
        }

        @JavascriptInterface
        public String __mm_method_handler(String method, String data) {
            Method[] methods = this.getClass().getMethods();
            for (Method meth : methods) {
                if (meth.getName().equals(method)) {
                    try {
                        JSONObject obj = new JSONObject(data);
                        Object[] params = new Object[obj.length()];
                        for (int uc=0; uc<obj.length();uc++) {
                            params[uc] = obj.get(uc + "");
                            if (params[uc].toString().startsWith("__mm_method_")) {
                                params[uc] = new JSCallback(caller, wb, params[uc].toString());
                            }
                        }
                        Object ret = meth.invoke(this, params);
                        JSONObject jsr = new JSONObject();
                        jsr.put("value", ret);
                        return jsr.toString();
                    } catch (JSONException e) {
                        e.printStackTrace();
                    } catch (IllegalAccessException e) {
                        e.printStackTrace();
                    } catch (InvocationTargetException e) {
                        e.printStackTrace();
                    }
                    return "";
                }
            }
            return "";
        }

        //PUBLIC METHODS HERE

        public int kkk (String s, int s1, int s2, final JSCallback uc) {
            Log.e("JSInterface",(s1+s2)+" = goof kkk "+s);
            uc.call("AAAAAAAAAAAAAAAAAA");
            final int[] ix = {1};
            new Thread(new Runnable() {
                public void run(){
                    while (ix[0] <20) {
                        try {
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        uc.call("AAAAAAAAAAAAAAAAAA" + ix[0]);
                        ix[0]++;
                    }
                }
            }).start();

            return 9;
        }

      //sample console output for this call:
      /*
      Android.kkk("ayy",1,2,function(a){console.log("bbbaaaaaaaaaaabbbbb"+a)})
      9
      (logcat) >>> E/JSInterface: 3 = goof kkk ayy
      VM30:1 bbbaaaaaaaaaaabbbbbAAAAAAAAAAAAAAAAAA
      VM30:1 bbbaaaaaaaaaaabbbbbAAAAAAAAAAAAAAAAAA1 (+1.000s)
      VM30:1 bbbaaaaaaaaaaabbbbbAAAAAAAAAAAAAAAAAA2 (+1.000s)
      VM30:1 bbbaaaaaaaaaaabbbbbAAAAAAAAAAAAAAAAAA3 (+1.000s)
      ...
      */

    }
}
	//How it works: all the script relies on a tiny javascript stub injected to webView's document that uses Proxy api and json serialicing stuff. Calls to our internal objects are proxified to a single method "__mm_handle_method", that using reflection find the target method and populate arguments exchanged in json, plus a custom interface for methods passed as argument.

	package es.pabloko.webviewbridge;

	import android.app.Activity;
	import android.content.Context;
	import android.support.v7.app.AppCompatActivity;
	import android.os.Bundle;
	import android.util.Log;
	import android.webkit.JavascriptInterface;
	import android.webkit.WebView;
	import org.json.JSONArray;
	import org.json.JSONException;
	import org.json.JSONObject;
	import java.lang.reflect.InvocationTargetException;
	import java.lang.reflect.Method;

	public class MainActivity extends AppCompatActivity {
	private String JSINTERFACE="Android";
	@Override
	protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	//setContentView(R.layout.activity_main);
	//WebView webView = findViewById(R.id.web);
	WebView webView = new WebView(this);
	webView.getSettings().setJavaScriptEnabled(true);
	webView.addJavascriptInterface(new JSInterface(this, webView, JSINTERFACE), JSINTERFACE+"_stub");
	String html = "<!DOCTYPE html><html><head><meta charset=\"utf-8\"><script>"
	+ "var __mm_cb={};function __mm_guid(){function _(){return Math.floor(65536*(1+Math.random())).toString(16).substring(1)}return\"__mm_method_\"+_()+_()+\"-\"+_()+\"-\"+_()+\"-\"+_()+\"-\"+_()+_()+_()}function __mm_callback(){var _=Array.from(arguments),n=_.shift();__mm_cb[n]&&__mm_cb[n].apply(null,_)}var __mm_method_handler="+JSINTERFACE+"_stub.__mm_method_handler.bind("+JSINTERFACE+"_stub),"+JSINTERFACE+"=new Proxy("+JSINTERFACE+"_stub,{get:function(_,r){return function(){for(var _=0;_<arguments.length;_++)if(\"[object Function]\"==={}.toString.call(arguments[_])){var n=__mm_guid();\"\"!=arguments[_].name&&(n=\"__mm_method_\"+arguments[_].name),__mm_cb[n]=arguments[_],arguments[_]=n}var m=__mm_method_handler(r,JSON.stringify(arguments));return JSON.parse(m).value}}});"
	+ "</script></head><body>Android WebView JavascriptInterface Test</body></html>";
	webView.loadData(html, "text/html", "UTF-8");
	WebView.setWebContentsDebuggingEnabled(true);
	setContentView(webView);
	}

	public class JSCallback {
	private Context caller;
	private WebView wb;
	private String guid;
	public JSCallback(Context caller, WebView wb, String guid) {
	this.caller = caller;
	this.wb=wb;
	this.guid=guid;
	}
	public void call(Object... o) {
	StringBuilder stringBuilder = new StringBuilder();
	stringBuilder.append("try{");
	String separator = "";
	if (guid.startsWith("__mm_method_")) {
	stringBuilder.append("__mm_callback");
	stringBuilder.append("(");
	stringBuilder.append("'" + guid + "'");
	separator = ",";
	} else {
	stringBuilder.append(guid);
	stringBuilder.append("(");
	}
	for (Object param : o) {
	stringBuilder.append(separator);
	separator = ",";
	if (param instanceof String) {
	stringBuilder.append("'");
	stringBuilder.append(((String) param).replace("'", "\'"));
	stringBuilder.append("'");
	} else
	stringBuilder.append(param);
	}
	stringBuilder.append(")}catch(error){console.error(error.message);}");
	final String call = stringBuilder.toString();
	((Activity)caller).runOnUiThread(new Runnable() {
	@Override
	public void run() {
	if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT) {
	wb.evaluateJavascript(call, null);
	} else {
	wb.loadUrl("javascript:" + call);
	}
	}
	});
	}
	}

	public class JSInterface {
	private Context caller;
	private WebView wb;
	private String jsinterfacename;

	public JSInterface(Context caller, WebView wb, String jsc) {
	this.wb = wb;
	this.jsinterfacename = jsc;
	this.caller = caller;
	}

	@JavascriptInterface
	public String __mm_method_handler(String method, String data) {
	Method[] methods = this.getClass().getMethods();
	for (Method meth : methods) {
	if (meth.getName().equals(method)) {
	try {
	JSONObject obj = new JSONObject(data);
	Object[] params = new Object[obj.length()];
	for (int uc=0; uc<obj.length();uc++) {
	params[uc] = obj.get(uc + "");
	if (params[uc].toString().startsWith("__mm_method_")) {
	params[uc] = new JSCallback(caller, wb, params[uc].toString());
	}
	}
	Object ret = meth.invoke(this, params);
	JSONObject jsr = new JSONObject();
	jsr.put("value", ret);
	return jsr.toString();
	} catch (JSONException e) {
	e.printStackTrace();
	} catch (IllegalAccessException e) {
	e.printStackTrace();
	} catch (InvocationTargetException e) {
	e.printStackTrace();
	}
	return "";
	}
	}
	return "";
	}

	//PUBLIC METHODS HERE

	public int kkk (String s, int s1, int s2, final JSCallback uc) {
	Log.e("JSInterface",(s1+s2)+" = goof kkk "+s);
	uc.call("AAAAAAAAAAAAAAAAAA");
	final int[] ix = {1};
	new Thread(new Runnable() {
	public void run(){
	while (ix[0] <20) {
	try {
	Thread.sleep(1000);
	} catch (InterruptedException e) {
	e.printStackTrace();
	}
	uc.call("AAAAAAAAAAAAAAAAAA" + ix[0]);
	ix[0]++;
	}
	}
	}).start();

	return 9;
	}

	//sample console output for this call:
	/*
	Android.kkk("ayy",1,2,function(a){console.log("bbbaaaaaaaaaaabbbbb"+a)})
	9
	(logcat) >>> E/JSInterface: 3 = goof kkk ayy
	VM30:1 bbbaaaaaaaaaaabbbbbAAAAAAAAAAAAAAAAAA
	VM30:1 bbbaaaaaaaaaaabbbbbAAAAAAAAAAAAAAAAAA1 (+1.000s)
	VM30:1 bbbaaaaaaaaaaabbbbbAAAAAAAAAAAAAAAAAA2 (+1.000s)
	VM30:1 bbbaaaaaaaaaaabbbbbAAAAAAAAAAAAAAAAAA3 (+1.000s)
	...
	*/

	}
	}