我们如何在我们的 android 应用程序中执行 javascript 函数并获取返回值？
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How we can execute a javascript function and get a return value in our android application?
提问by Praful Bhatnagar
How we can execute a javascript function and get a return value in our android appplication ?
我们如何执行 javascript 函数并在我们的 android 应用程序中获取返回值？
We want to execute a javascript on a button press event, we need to pass parameters to the script and get return values, So we are using "WebChromeClient" to implement this, But we got Exception is "SyntaxError: Parse error at undefined:1"
我们想在按钮按下事件上执行一个 javascript，我们需要将参数传递给脚本并获取返回值，所以我们使用“WebChromeClient”来实现这一点，但我们得到的异常是“SyntaxError: Parse error at undefined:1 ”
Following is my code
以下是我的代码
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.webkit.JsResult;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
public class FirstTab extends Activity
{
private WebView webView;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.regis);
try{
webView = (WebView) findViewById(R.id.webView1);
webView.getSettings().setJavaScriptEnabled(true);
webView.setWebChromeClient(new MyWebChromeClient());
String customHtml = "<html><head><title>iSales</title><script type=\"text/javascript\"> function fieldsOnDelete(){ var x=123; return \"JIJO\"; } </script></head><body>hi</body></html>";
webView.loadData(customHtml, "text/html","UTF-8");
}catch(Exception e)
{
Log.v("JAC LOG",e.toString());
}
}
public void onResume()
{
super.onResume();
final Button button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
try{
webView.loadUrl("javascript:alert(javascript:fieldsOnDelete())");
}
catch(Exception e)
{
Log.v("JAC LOG",e.toString());
}
}
});
}
final class MyWebChromeClient extends WebChromeClient {
@Override
public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
Log.v("LogTag", message);
result.confirm();
return true;
}
}
}
回答by Praful Bhatnagar
you can use mWebView.loadUrl("javascript:checkName");to call the method...
您可以使用 mWebView.loadUrl("javascript:checkName");调用该方法...
Then you can use addJavascriptInterface()to add a Java object to the Javascript environment. Have your Java script call a method on that Java object to supply its "return value".
然后您可以使用addJavascriptInterface()将 Java 对象添加到 Javascript 环境中。让您的 Java 脚本调用该 Java 对象上的方法以提供其“返回值”。
EDIT1: Or you can use following hack:
EDIT1：或者您可以使用以下技巧：
Add this Client to your WebView:
将此客户端添加到您的 WebView：
final class MyWebChromeClient extends WebChromeClient {
@Override
public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
Log.d("LogTag", message);
result.confirm();
return true;
}
}
Now in your java script call do:
现在在您的 java 脚本调用中执行以下操作：
webView.loadUrl("javascript:alert(functionThatReturnsSomething)");
Now in the onJsAlert call "message" will contain the returned value.
现在在 onJsAlert 调用中“ message”将包含返回值。
Edit2:
编辑2：
So it does not work if we call javascript method just after call to load the URL since the page loads take time. So I created a test program to test that...
因此，如果我们在调用加载 URL 后立即调用 javascript 方法，则它不起作用，因为页面加载需要时间。所以我创建了一个测试程序来测试......
Following is my html file (named test.html) store in the assets folder:
以下是我的 html 文件（名为 test.html）存储在资产文件夹中：
<html>
<head>
<script language="javascript">
function fieldsOnDelete(message) {
alert("i am called with " + message);
window.myjava.returnValue(message + " JIJO");
}
</script>
<title>iSales android</title>
</head>
<body></body>
</html>
</body>
</html>
Following is my java class that would get that i would add to java script as interface and it would receive the return value:
以下是我的 java 类，它将作为接口添加到 java 脚本中，并且它将接收返回值：
public class MyJS {
public void returnValue(String string){
Log.d(this.getClass().getSimpleName(), string);
}
}
And following is my activity class:
以下是我的活动课：
public class CheckWebView extends Activity {
private WebView webView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_check_web_view);
webView = (WebView) findViewById(R.id.webview);
webView.setWebChromeClient(new WebChromeClient() {
@Override
public void onConsoleMessage(String message, int lineNumber,
String sourceID) {
super.onConsoleMessage(message, lineNumber, sourceID);
Log.d(this.getClass().getCanonicalName(), "message " + message
+ " :::line number " + lineNumber + " :::source id "
+ sourceID);
}
@Override
public boolean onConsoleMessage(ConsoleMessage consoleMessage) {
// TODO Auto-generated method stub
onConsoleMessage(consoleMessage.message(),
consoleMessage.lineNumber(), consoleMessage.sourceId());
Log.d(this.getClass().getCanonicalName(), "message::::: "
+ consoleMessage.message());
return super.onConsoleMessage(consoleMessage);
}
});
webView.addJavascriptInterface(new MyJS(), "myjava");
webView.getSettings().setJavaScriptEnabled(true);
webView.getSettings().setPluginsEnabled(true);
webView.getSettings().setAllowFileAccess(true);
webView.loadUrl("file:///android_asset/test.html");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_check_web_view, menu);
return true;
}
/* (non-Javadoc)
* @see android.app.Activity#onOptionsItemSelected(android.view.MenuItem)
*/
@Override
public boolean onOptionsItemSelected(MenuItem item) {
webView.loadUrl("javascript:fieldsOnDelete('name');");
return super.onOptionsItemSelected(item);
}
}
The key here is that there should be some time interval between the call to load html file from assets folder and the call to javascript:method. Here I am calling it from onOptionsItemSelectedand it is working fine.. if I move the webView.loadUrl("javascript:fieldsOnDelete('name');");to the end of the onCreate() method the it shows the error that it can not find fieldsOnDelete()method...
这里的关键是在调用从资产文件夹加载 html 文件和调用javascript:method. 我在这里调用它onOptionsItemSelected并且它工作正常..如果我将 移动 webView.loadUrl("javascript:fieldsOnDelete('name');");到 onCreate() 方法的末尾，它会显示它无法找到fieldsOnDelete()方法的错误......
Hope it Helps...
希望能帮助到你...
EDIT3:
编辑3：
Replace following in your code
在您的代码中替换以下内容
webView.loadUrl("javascript:alert(javascript:fieldsOnDelete())");
with
和
webView.loadUrl("javascript:alert(fieldsOnDelete())");
and try...
并尝试...
回答by Matt Gaunt
In Android KitKat there is a new method evaluateJavascript that has a callback for a return value. The callback returns a JSON value, object or array depending on what you return.
在 Android KitKat 中有一个新方法 evaluateJavascript 有一个返回值的回调。回调根据您返回的内容返回 JSON 值、对象或数组。
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
// In KitKat+ you should use the evaluateJavascript method
mWebView.evaluateJavascript(javascript, new ValueCallback<String>() {
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@Override
public void onReceiveValue(String s) {
JsonReader reader = new JsonReader(new StringReader(s));
// Must set lenient to parse single values
reader.setLenient(true);
try {
if(reader.peek() != JsonToken.NULL) {
if(reader.peek() == JsonToken.STRING) {
String msg = reader.nextString();
if(msg != null) {
Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_LONG).show();
}
}
}
} catch (IOException e) {
Log.e("TAG", "MainActivity: IOException", e);
} finally {
try {
reader.close();
} catch (IOException e) {
// NOOP
}
}
}
});
}
You can see a full example here: https://github.com/GoogleChrome/chromium-webview-samples/tree/master/jsinterface-example
你可以在这里看到一个完整的例子：https: //github.com/GoogleChrome/chromium-webview-samples/tree/master/jsinterface-example
