自从我上一次 Java 课程以来已经有好几年了，更不用说在工作中从未写过 JAVA 了。
无论如何，我试图让这个 Cordova 应用程序在执行 javascript html + 初始 AJAX 调用时在启动屏幕上呈现加载小部件。
我已经接受了这篇文章的建议，但我没有做正确的事情......每个DroidGap.java源都有 appView，所以它不能为空。事实上，我不知道这里指向 null 的是什么。也许我把这段代码放在了错误的地方？
希望我有更多时间在这里深入研究......如果有人有一些建议，我会全神贯注，好吧，无论如何都要全神贯注。
有这个pastebin 帖子看起来与上面的帖子相同，所以我考虑在 onCreate 之外使用进度条代码无济于事。
package com.Project.MainActivity;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.widget.ProgressBar;
import org.apache.cordova.*;
public class MainActivity extends DroidGap
{
final Activity activity = this;
private ProgressBar progessBar1;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
View footer = View.inflate(getContext(), R.layout.main, root);
root.addView(footer);
progessBar1 = (ProgressBar) findViewById(R.id.progressBar1);
this.appView.setWebChromeClient(new WebChromeClient() {
public void onProgressChanged(WebView view, int progress) {
progessBar1.setProgress(progress * 1000);
if(progress < 100 && progessBar1.getVisibility() == ProgressBar.GONE) {
progessBar1.setVisibility(ProgressBar.VISIBLE);
}
progessBar1.setProgress(progress);
if(progress == 100) {
progessBar1.setVisibility(ProgressBar.GONE);
}
Log.d("Progress", progress+"");
}
});
super.setStringProperty("loadingDialog", "Wait, Loading...");
// Set by <content src="index.html" /> in config.xml
super.loadUrl("file:///android_asset/www/index.html");
}
}
此代码产生输出：
05-22 10:13:27.238: E/UpdateReceiver(11872): ACTION_PACKAGE_REMOVED
05-22 10:13:29.988: E/dalvikvm(14200): could not disable core file generation for pid 14200: Operation not permitted
05-22 09:37:01.394: E/AndroidRuntime(13370): FATAL EXCEPTION: main
05-22 09:37:01.394: E/AndroidRuntime(13370): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.Project.MainActivity/com.Project.MainActivity.MainActivity}: java.lang.NullPointerException
05-22 09:37:01.394: E/AndroidRuntime(13370): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1702)
05-22 09:37:01.394: E/AndroidRuntime(13370): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1722)
05-22 09:37:01.394: E/AndroidRuntime(13370): at android.app.ActivityThread.access$1500(ActivityThread.java:124)
05-22 09:37:01.394: E/AndroidRuntime(13370): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:974)
05-22 09:37:01.394: E/AndroidRuntime(13370): at android.os.Handler.dispatchMessage(Handler.java:99)
05-22 09:37:01.394: E/AndroidRuntime(13370): at android.os.Looper.loop(Looper.java:130)
05-22 09:37:01.394: E/AndroidRuntime(13370): at android.app.ActivityThread.main(ActivityThread.java:3821)
05-22 09:37:01.394: E/AndroidRuntime(13370): at java.lang.reflect.Method.invokeNative(Native Method)
05-22 09:37:01.394: E/AndroidRuntime(13370): at java.lang.reflect.Method.invoke(Method.java:507)
05-22 09:37:01.394: E/AndroidRuntime(13370): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
05-22 09:37:01.394: E/AndroidRuntime(13370): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
05-22 09:37:01.394: E/AndroidRuntime(13370): at dalvik.system.NativeStart.main(Native Method)
05-22 09:37:01.394: E/AndroidRuntime(13370): Caused by: java.lang.NullPointerException
05-22 09:37:01.394: E/AndroidRuntime(13370): at com.Project.MainActivity.MainActivity.onCreate(MainActivity.java:48)
05-22 09:37:01.394: E/AndroidRuntime(13370): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-22 09:37:01.394: E/AndroidRuntime(13370): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1666)
05-22 09:37:01.394: E/AndroidRuntime(13370): ... 11 more
资源/布局/main.xml ...
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<ProgressBar
android:id="@+id/progressBar1"
style="@android:style/Widget.ProgressBar.Horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:maxHeight="10dip"
android:minHeight="10dip" />
</LinearLayout>
this.appView 为空，但不应按照 super.onCreate(...) 调用，如此处所示：
313 /**
314 * Create and initialize web container with default web view objects.
315 */
316 public void init() {
317 CordovaWebView webView = new CordovaWebView(CordovaActivity.this);
318 CordovaWebViewClient webViewClient;
319 if(android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.HONEYCOMB)
320 {
321 webViewClient = new CordovaWebViewClient(this, webView);
322 }
323 else
324 {
325 webViewClient = new IceCreamCordovaWebViewClient(this, webView);
326 }
327 this.init(webView, webViewClient, new CordovaChromeClient(this, webView));
328 }
329
330 /**
331 * Initialize web container with web view objects.
332 *
333 * @param webView
334 * @param webViewClient
335 * @param webChromeClient
336 */
337 @SuppressLint("NewApi")
338 public void init(CordovaWebView webView, CordovaWebViewClient webViewClient, CordovaChromeClient webChromeClient) {
339 LOG.d(TAG, "DroidGap.init()");
340
341 // Set up web container
342 this.appView = webView;
343 this.appView.setId(100);
344
345 this.appView.setWebViewClient(webViewClient);
346 this.appView.setWebChromeClient(webChromeClient);