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[英]NullPointerException when cancel progressDialog to go back another activity
[英]Using ProgressDialog when finish() on Activity, NullPointerException
我要注册一个简单的后台任务,为用户显示进度对话框。 问题在于,我相信我会收到NullPointerException
,因为在意图中启动的第二个活动是以某种方式在dialogProgressHide();
之前被调用的dialogProgressHide();
方法,即使该代码在代码中排在第一位,因此上下文不同且进度返回null导致错误。
book.saveInBackground(new SaveCallback()
{
@Override
public void done(ParseException e) {
if (e == null)
{
dialogProgressHide();
Toast.makeText(getApplicationContext(), "Your book was posted correctly!", Toast.LENGTH_LONG).show();
finish();
}
else
{
Toast.makeText(getApplicationContext(), "An error has occured: " + e + "\n" + "Please try again!", Toast.LENGTH_LONG).show();
dialogProgressHide();
}
}
});
我可能是错的,但这对我来说很有意义,问题是我该如何解决? 我只是希望对话框在完成活动之前消失,因此当上下文中不再有进度时,它不会尝试进行操作。
如果需要,这是对话方法:
private void dialogProgressShow() {
mDialog = new ProgressDialog(this);
mDialog.setMessage("One moment please while we post your book.");
mDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
mDialog.show();
}
private void dialogProgressHide() {
if (mDialog.isShowing())
{
mDialog.dismiss();
mDialog = null;
}
}
}
LOGCAT:
03-25 17:12:44.862: E/AndroidRuntime(16528): FATAL EXCEPTION: main
03-25 17:12:44.862: E/AndroidRuntime(16528): Process: com.jameswilson.booksale, PID: 16528
03-25 17:12:44.862: E/AndroidRuntime(16528): java.lang.NullPointerException
03-25 17:12:44.862: E/AndroidRuntime(16528): at com.jameswilson.booksale.PostBookActivity.dialogProgressHide(PostBookActivity.java:255)
03-25 17:12:44.862: E/AndroidRuntime(16528): at com.jameswilson.booksale.PostBookActivity.access$1(PostBookActivity.java:254)
03-25 17:12:44.862: E/AndroidRuntime(16528): at com.jameswilson.booksale.PostBookActivity$2$1.done(PostBookActivity.java:144)
03-25 17:12:44.862: E/AndroidRuntime(16528): at com.parse.SaveCallback.internalDone(SaveCallback.java:39)
03-25 17:12:44.862: E/AndroidRuntime(16528): at com.parse.SaveCallback.internalDone(SaveCallback.java:27)
03-25 17:12:44.862: E/AndroidRuntime(16528): at com.parse.Parse$6$1.run(Parse.java:846)
03-25 17:12:44.862: E/AndroidRuntime(16528): at android.os.Handler.handleCallback(Handler.java:733)
03-25 17:12:44.862: E/AndroidRuntime(16528): at android.os.Handler.dispatchMessage(Handler.java:95)
03-25 17:12:44.862: E/AndroidRuntime(16528): at android.os.Looper.loop(Looper.java:136)
03-25 17:12:44.862: E/AndroidRuntime(16528): at android.app.ActivityThread.main(ActivityThread.java:5017)
03-25 17:12:44.862: E/AndroidRuntime(16528): at java.lang.reflect.Method.invokeNative(Native Method)
03-25 17:12:44.862: E/AndroidRuntime(16528): at java.lang.reflect.Method.invoke(Method.java:515)
03-25 17:12:44.862: E/AndroidRuntime(16528): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-25 17:12:44.862: E/AndroidRuntime(16528): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-25 17:12:44.862: E/AndroidRuntime(16528): at dalvik.system.NativeStart.main(Native Method)
在尝试关闭对话框引用之前,先检查它是否为空
private void dialogProgressHide() {
if (mDialog != null && mDialog.isShowing())
{
mDialog.dismiss();
mDialog = null;
}
}
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