android通过WebView的evaluateJavascript()调用JS

public class MainActivity extends Activity {WebView webView;Button buttonLeft, buttonRight;&＃64;Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);webView &＃61; findViewById(R.id.webview);buttonLeft &＃61; findViewById(R.id.btnLeft);buttonRight &＃61; findViewById(R.id.btnRight);WebSettings webSettings &＃61; webView.getSettings();//允许使用JSwebSettings.setJavascriptEnabled(true);// 设置允许JS弹窗webSettings.setJavascriptCanOpenWindowsAutomatically(true);webView.loadUrl("file:///android_asset/index.html");buttonLeft.setOnClickListener(new View.OnClickListener() {&＃64;Overridepublic void onClick(View view) {webView.post(new Runnable() {&＃64;Overridepublic void run() {webView.evaluateJavascript("Javascript:callJS()", new ValueCallback() {&＃64;Overridepublic void onReceiveValue(String s) {//将button显示的文字改成JS返回的字符串buttonLeft.setText(s);}});}});}});webView.setWebChromeClient(new WebChromeClient() {&＃64;Overridepublic boolean onJsAlert(WebView view, String url, String message, final JsResult result) {AlertDialog.Builder b &＃61; new AlertDialog.Builder(MainActivity.this);b.setTitle("alert1");b.setMessage(message);b.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {&＃64;Overridepublic void onClick(DialogInterface dialogInterface, int i) {result.confirm();}});b.setCancelable(false);b.create().show();return true;}});}
}