我正在尝试编写android webview代码来从url中加载来自jason文件的数据。但是，我注意到初始时间页面上没有显示数据，但是如果我单击按钮加载/刷新数据再次页面（不确定是否是因为刷新或重新加载），则会成功显示。我检查了日志文件。第一次单击将以下内容输出到日志中。
08-17 16:07:38.784: V/webview(17435): singleCursorHandlerTouchEvent -getEditableSupport FASLE
08-17 16:07:39.184: V/webview(17435): doShortPress : mNativeClass - 2089760 mPreventDefault - 2
08-17 16:07:41.777: V/webview(17435): singleCursorHandlerTouchEvent -getEditableSupport FASLE
08-17 16:07:42.187: V/webview(17435): doShortPress : mNativeClass - 2089760 mPreventDefault - 2
08-17 16:07:42.588: D/dalvikvm(17435): GC_CONCURRENT freed 375K, 46% free 3455K/6343K, external 377K/1281K, paused 2ms+2ms
第二次运行时会在log中显示以下文本，我们可以看到输出到最后一行日志的已加载字符串数据。
08-17 16:07:51.837: V/webview(17435): singleCursorHandlerTouchEvent -getEditableSupport FASLE
08-17 16:07:52.247: V/webview(17435): doShortPress : mNativeClass - 2089760 mPreventDefault - 2
08-17 16:07:55.901: V/webview(17435): singleCursorHandlerTouchEvent -getEditableSupport FASLE
08-17 16:07:56.301: V/webview(17435): doShortPress : mNativeClass - 2089760 mPreventDefault - 2
08-17 16:07:56.501: D/dalvikvm(17435): GC_FOR_MALLOC freed 117K, 46% free 3472K/6343K, external 377K/1281K, paused 15ms
08-17 16:07:56.501: I/dalvikvm-heap(17435): Grow heap (frag case) to 6.195MB for 87396-byte allocation
08-17 16:07:56.521: D/dalvikvm(17435): GC_FOR_MALLOC freed 32K, 46% free 3525K/6471K, external 377K/1281K, paused 16ms
08-17 16:07:56.591: I/my call:(17435): <ul data-role='listview'><li>abc<p style='font-size:1 font-color:grey'>2014-08-11</p></li><li>def<p style='font-size:1 font-color:grey'>2014-08-14</p></li><li>fgh<p style='font-size:1 font-color:grey'>2014-08-14</p></li><li>hijk<p style='font-size:1 font-color:grey'>2014-08-15</p></li></ul>
有人能说出为什么第一次没带数据吗？请帮忙。感谢。
以下是我的活动代码。
@SuppressLint("SetJavaScriptEnabled")
public class MessageActivity extends Activity {
WebView mWebView;
public static String liststr = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_message);
mWebView = (WebView) findViewById(R.id.webview);
mWebView.setWebViewClient(new WebViewClient() {
public boolean shouldOverrideUrlLoading(WebView view, String url) {
return false;
}
});
mWebView.setVerticalScrollBarEnabled(false);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.getSettings().setDomStorageEnabled(true);
mWebView.addJavascriptInterface(new JavaScriptInterface(), "jsinterface");
mWebView.loadUrl("file:///android_asset/index.html");
}
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK) && mWebView.canGoBack()) {
mWebView.destroy();
finish();
mWebView.destroy();
return true;
}
else if (keyCode == KeyEvent.KEYCODE_BACK){
mWebView.destroy();
finish();
mWebView.destroy();
}
return super.onKeyDown(keyCode, event);
}
private class LongRunningGetIO extends AsyncTask <Void, Void, String> {
protected String getASCIIContentFromEntity(HttpEntity entity) throws IllegalStateException, IOException {
InputStream in = entity.getContent();
StringBuffer out = new StringBuffer();
int n = 1;
while (n>0) {
byte[] b = new byte[4096];
n = in.read(b);
if (n>0) out.append(new String(b, 0, n));
}
return out.toString();
}
@Override
protected String doInBackground(Void... params) {
HttpClient httpClient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
HttpGet httpGet = new HttpGet("http://****/Post.json");
String text = null;
try {
HttpResponse response = httpClient.execute(httpGet, localContext);
HttpEntity entity = response.getEntity();
text = getASCIIContentFromEntity(entity);
} catch (Exception e) {
return e.getLocalizedMessage();
}
return text;
}
protected void onPostExecute(String results) {
getJsonData(results);
}
protected void getJsonData (String jsonstr) {
JSONArray postarr = new JSONArray();
liststr = "<ul data-role='listview'>";
try {
JSONObject posts = (new JSONObject(jsonstr).getJSONObject("posts"));
postarr = posts.getJSONArray("post");
for (int i=0; i<postarr.length(); i++) {
JSONObject p = postarr.getJSONObject(i);
liststr += "<li>";
liststr += p.getString("title");
liststr += "<p style='font-size:1 font-color:grey'>";
liststr += p.getString("date");
liststr += "</p>";
liststr += "</li>";
}
liststr += "</ul>";
} catch (JSONException e) {
e.printStackTrace();
}
}
}
public class JavaScriptInterface {
String str;
@JavascriptInterface
public String getPostValue() {
new LongRunningGetIO().execute();
this.str = liststr;
return str;
}
}
}
我的index.html页面。
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>LoadPageTest</title>
<link rel="stylesheet" href="http://fonts.googleapis.com/css?family=Open+Sans:300,400,700">
<link rel="stylesheet" href="./css/customizedstyle.css">
<link rel="stylesheet" href="./css/themes/default/jquery.mobile-1.4.3.min.css">
<link rel="stylesheet" href="./css/jqm-demos.css">
<script src="./js/jquery.js"></script>
<script scr="./js/customizedjs.js"></script>
<script src="./js/jquery.mobile-1.4.3.min.js"></script>
<script>
$( document ).on( "pagecreate", "#demo-page", function() {
$( document ).on( "swipeleft swiperight", "#demo-page", function( e ) {
if ( $( ".ui-page-active" ).jqmData( "panel" ) !== "open" ) {
if ( e.type === "swipeleft" ) {
$( "#right-panel" ).panel( "open" );
}
}
});
});
</script>
<style type="text/css">
body {
overflow:hidden;
}
</style>
</head>
<body style= "overflow:hidden" scrolling="no">
<style type="text/css">
body {
overflow:hidden;
}
</style>
<div data-role="page" id="main-page" style= "overflow:hidden" scrolling="no">
<div role="main" class="ui-content" id ="maindiv" style= "overflow: auto">
Will load diff pages here.
</div><!-- /content -->
<div data-role="panel" id="left-panel" data-theme="b">
<ul data-role="listview" data-icon="false" id="menu">
<li>
<a href="#" id = "btnA" data-rel="close">Go Page A <img src="./images/icona.png" class="ui-li-thumb"/>
</li>
</ul>
</div><!-- /panel -->
<script type="text/javascript">
$("#btnA").on("click", function(){
var listposts = window.jsinterface.getPostValue();
document.getElementById( "maindiv" ).innerHTML = "<html><body>"+listposts+"</body></html>";
});
</script>
</div><!-- /page -->
</body>
</html>