使用javascript接口进行表单打印

Question

我使用webview提交html表单和相同的表单按钮来打印表单。

但是当我使用界面时会出现某种问题。 Toast消息显示但不创建打印作业create WebPrintJob(myWebView);

你可以帮帮我吗？

Activity.Java

package mascoli.printweb;

import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.print.PrintJob;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.KeyEvent;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.view.LayoutInflater;
import android.webkit.JavascriptInterface;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.os.Build;
import android.print.PrintAttributes;
import android.print.PrintDocumentAdapter;
import android.print.PrintManager;
import android.content.Context;
import android.webkit.WebViewClient;
import android.widget.Toast;


public class WebPrintActivity extends AppCompatActivity {

    WebView myWebView;

    @Override
    protected void onStart() {
        super.onStart();

        myWebView=(WebView)findViewById(R.id.myWebView);
        myWebView.setWebViewClient(new WebViewClient());
        myWebView.getSettings().getBuiltInZoomControls();
        myWebView.setInitialScale(139);
        myWebView.getSettings().setSaveFormData(false);
        myWebView.getSettings().setJavaScriptEnabled(true);

        WebSettings ws = myWebView.getSettings();
        ws.setJavaScriptEnabled(true);

        myWebView.getSettings().setJavaScriptEnabled(true);
        myWebView.addJavascriptInterface(new WebViewJavaScriptInterface(this), "app");


        myWebView.loadUrl("http://192.168.1.67/ford/web.html");

    }

    /*
     * JavaScript Interface. Web code can access methods in here
     * (as long as they have the @JavascriptInterface annotation)
     */
    public class WebViewJavaScriptInterface{

        private Context context;

        /*
         * Need a reference to the context in order to sent a post message
         */
        public WebViewJavaScriptInterface(Context context){
            this.context = context;
        }

        /*
         * This method can be called from Android. @JavascriptInterface
         * required after SDK version 17.
         */
        @JavascriptInterface
        public void makeToast(String message, boolean lengthLong){
            Toast.makeText(context, message, (lengthLong ? Toast.LENGTH_LONG : Toast.LENGTH_SHORT)).show();
            createWebPrintJob(myWebView); //PROBLEM HERE

        }
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_print:
                createWebPrintJob(myWebView);
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    public void createWebPrintJob(WebView webView) {

        PrintManager printManager = (PrintManager) this
                .getSystemService(Context.PRINT_SERVICE);

        PrintDocumentAdapter printAdapter =
                webView.createPrintDocumentAdapter();

        String jobName = " Print form";
        printManager.print(jobName, printAdapter,
                new PrintAttributes.Builder().build());
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_web_print);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_web_print, menu);
        return true;
    }
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {

        if (keyCode==KeyEvent.KEYCODE_BACK){
            if (myWebView.canGoBack()){
                myWebView.goBack();
                return true;
            }
            return super.onKeyDown(keyCode, event);
        }
        return super.onKeyDown(keyCode, event);
    }
}

Web.html

<!DOCTYPE html>
<html>
<head>
    <title>JavaScript View</title>

    <script type="text/javascript">

        function showToast(){
            var message = document.getElementById("message").value;
            var lengthLong = document.getElementById("length").checked;

            /* 
                Call the 'makeToast' method in the Java code. 
                'app' is specified in MainActivity.java when 
                adding the JavaScript interface. 
             */
             app.
            app.makeToast(message, lengthLong);
            return false;
        }

        /* 
            Call the 'showToast' method when the form gets 
            submitted (by pressing button or return key on keyboard). 
         */
        window.onload = function(){
            var form = document.getElementById("form");
            form.onsubmit = showToast;
        }
    </script>
</head>

<body>

<form id="form">
    Message: <input id="message" name="message" type="text"/><br />
    Long: <input id="length" name="length" type="checkbox" /><br />

    <input type="submit" value="Make Toast" />
</form>

</body>
</html>