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我寫一個應用程序中對此我允許用戶進行登陸，但每當我做點擊登錄按鈕讓不幸的是應用程序已經停止，錯誤：顯示java.lang.NullPointerException - 不幸的是應用程序已經停止
java.lang.NullPointerException
造成的：
DetailActivity，行號：
btnDisplay.setOnClickListener(new OnClickListener()
DetailActivity，行號：
showInfo();
logcat的說::
04-12 10:52:06.250: E/AndroidRuntime(991): FATAL EXCEPTION: main
04-12 10:52:06.250: E/AndroidRuntime(991): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.smart.restaurant.versionoct/com.smart.restaurant.versionoct.cart.DetailActivity}: java.lang.NullPointerException
04-12 10:52:06.250: E/AndroidRuntime(991): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
04-12 10:52:06.250: E/AndroidRuntime(991): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
04-12 10:52:06.250: E/AndroidRuntime(991): at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-12 10:52:06.250: E/AndroidRuntime(991): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-12 10:52:06.250: E/AndroidRuntime(991): at android.os.Handler.dispatchMessage(Handler.java:99)
04-12 10:52:06.250: E/AndroidRuntime(991): at android.os.Looper.loop(Looper.java:137)
04-12 10:52:06.250: E/AndroidRuntime(991): at android.app.ActivityThread.main(ActivityThread.java:5039)
04-12 10:52:06.250: E/AndroidRuntime(991): at java.lang.reflect.Method.invokeNative(Native Method)
04-12 10:52:06.250: E/AndroidRuntime(991): at java.lang.reflect.Method.invoke(Method.java:511)
04-12 10:52:06.250: E/AndroidRuntime(991): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-12 10:52:06.250: E/AndroidRuntime(991): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-12 10:52:06.250: E/AndroidRuntime(991): at dalvik.system.NativeStart.main(Native Method)
04-12 10:52:06.250: E/AndroidRuntime(991): Caused by: java.lang.NullPointerException
04-12 10:52:06.250: E/AndroidRuntime(991): at com.smart.restaurant.versionoct.cart.DetailActivity.showInfo(DetailActivity.java:127)
04-12 10:52:06.250: E/AndroidRuntime(991): at com.smart.restaurant.versionoct.cart.DetailActivity.onCreate(DetailActivity.java:62)
04-12 10:52:06.250: E/AndroidRuntime(991): at android.app.Activity.performCreate(Activity.java:5104)
04-12 10:52:06.250: E/AndroidRuntime(991): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
04-12 10:52:06.250: E/AndroidRuntime(991): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
04-12 10:52:06.250: E/AndroidRuntime(991): ... 11 more
LoginActivity.java：
// btnLogin
final Button btnLogin = (Button) findViewById(R.id.btnLogin);
// Perform action on click
btnLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String url = "http://ipaddress/checkLogin.php";
});
}
DetailActivity.java：
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_checkout_member);
btnDisplay = (ImageButton) findViewById(R.id.buttonSubmit);
}
});
}
activity_detail.xml：
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<include
android:id="@+id/header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
layout="@layout/header_checkout" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/textView1"
android:layout_alignBottom="@+id/textView1"
android:layout_marginLeft="46dp"
android:layout_toRightOf="@+id/textView1"
android:text="$"
android:layout_marginBottom="20dp"
android:textStyle="bold"
android:textAppearance="?android:attr/textAppearanceLarge" />
<RadioGroup
android:id="@+id/radioPayMode"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/radioUser"
android:layout_alignParentRight="true"
android:layout_below="@+id/textView1"
android:layout_toRightOf="@+id/radioUser"
android:background="@color/test4"
android:layout_marginTop="20dp"
android:orientation="horizontal" >
<RadioButton
android:id="@+id/radioCashOnDelivery"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:checked="true"
android:textStyle="italic"
android:text="Cash On Delivery"
android:layout_marginRight="2dp" />
<RadioButton
android:id="@+id/radioCreditCard"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_marginTop="8dp"
android:textStyle="italic"
android:text="Credit Card" />
</RadioGroup>
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/header"
android:layout_marginTop="10dp"
android:text="Amount to Pay:"
android:layout_marginLeft="10dp"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textStyle="italic" />
<TextView
android:id="@+id/total"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/radioPayMode"
android:layout_toRightOf="@+id/textView2"
android:text="0"
android:layout_marginLeft="2dp"
android:textAppearance="?android:attr/textAppearanceLarge" />
<ImageButton
android:id="@+id/btnSubmit"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignRight="@+id/textView2"
android:layout_marginBottom="22dp"
android:background="@drawable/place_button" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/radioPayMode"
android:text="Name"
android:layout_marginTop="10dp"
android:textStyle="bold"
android:layout_marginLeft="5dp"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/txtName"
android:layout_marginTop="10dp"
android:textStyle="bold"
android:layout_marginLeft="5dp"
android:text="Email ID"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/txtName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/textView3"
android:hint="Your Name Here"
android:maxLines="1"
android:layout_marginTop="1dp"
android:layout_marginLeft="10dp"
android:textAppearance="?android:attr/textAppearanceSmall" />
<TextView
android:id="@+id/txtEmail"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
android:hint="Your Email Here"
android:layout_below="@+id/textView4"
android:maxLines="1"
android:layout_marginTop="1dp"
android:layout_marginLeft="10dp"
android:textAppearance="?android:attr/textAppearanceSmall"/>
<TextView
android:id="@+id/textView5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView4"
android:layout_below="@+id/txtEmail"
android:layout_marginTop="10dp"
android:textStyle="bold"
android:text="Contact Number"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/txtTel"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_below="@+id/textView5"
android:hint="Your Mobile Number"
android:layout_marginTop="1dp"
android:layout_marginLeft="10dp"
android:maxLines="1"
android:textAppearance="?android:attr/textAppearanceSmall" />
<TextView
android:id="@+id/textView6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView5"
android:layout_below="@+id/txtTel"
android:layout_marginTop="10dp"
android:text="Shipping Address"
android:textStyle="bold"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/txtAddress"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/textView6"
android:gravity="top"
android:hint="Your Address Here"
android:inputType="textMultiLine"
android:layout_marginTop="1dp"
android:maxLines="3"
android:layout_marginRight="10dp"
android:layout_marginLeft="10dp"
android:textAppearance="?android:attr/textAppearanceSmall" />
</RelativeLayout>
什麼是線127 showInfo（）？ – Zyerah
發佈您的詳細信息活動佈局xml – Dinesh
@Telthien我已經將該方法代碼放在DetailActivity.java中 – ASMUIRTI