自从我上一次Java课程以来已经有好几年了，更不用说从未在工作中编写过JAVA了。
无论如何，我正在尝试使用这个Cordova应用程序在启动屏幕上渲染加载小部件，同时执行javascript html +初始AJAX调用。
我接受了来自this post的建议，但我没有做正确的事情... appView是每个DroidGap.java来源，因此不能为空。实际上我不知道这里指向null的是什么..也许我在错误的地方有这个代码？
希望我有更多时间潜入这里的事情......如果有人有一些建议，我会全力以赴，好吧，无论如何都是所有的目光。
这个pastebin post看起来与上面的相同，所以我认为在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");
}
}
此代码生成输出：
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
res / layouts / 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null，但它不应该按照here看到的super.onCreate（...）调用：
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);
答案 0 :(得分：4)
好吧，NullPointerException非常简单：变量为null，你正试图访问它上面的字段/方法。
如果第48行是
this.appView.setWebChromeClient(new WebChromeClient() {
appView很有可能为空。
我不知道Cordova，但您应该查看DroidGap生命周期并查看Javadoc中提供的示例。
似乎你需要在某个时候调用super.init（）来初始化appView。