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社区首页 >问答首页 >在android studio中使用自定义适配器时出现"java.lang.NullPointerException“错误

问在android studio中使用自定义适配器时出现"java.lang.NullPointerException“错误
EN

Stack Overflow用户
提问于 2018-08-08 01:48:50
回答 1查看 68关注 0票数 -1

当我尝试运行此适配器代码时，我得到java.lang.NullPointerException.我使用调试器检查错误。此外，我还检查了变量currentbuildingnumber和BuildingNumber以及打印的日志语句

代码语言：javascript
复制
08-07 18:44:25.528 12998-12998/com.example.mustafa.progressupdate V/E1: Adapter Building Number is E1
Activity Building Number is E1

所以我认为问题出在if语句中...然而，我不知道为什么它不能工作，两个变量都定义了，并且语句是真的！

适配器代码

代码语言：javascript
复制
public class ActivityAdapter extends ArrayAdapter<Activity> {

/**
 * Resource ID for the background color for this list of words
 */
public Activity currentActivity;
public String BuildingNumber;
public String currentbuildingnumber;

public ActivityAdapter(Context context, ArrayList<Activity> Activities, String adapterbuildingnumber) {
    super(context, 0, Activities);
    // This is the Building number of the Clicked Building
    currentbuildingnumber = adapterbuildingnumber;
    // This is the Building number of the Activity
    BuildingNumber = currentActivity.getBuildingNumber();
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    Log.v("E1", "Adapter Building Number is " + currentbuildingnumber);
    Log.v("E1", "Activity Building Number is " + BuildingNumber);

    View v = convertView;

    if(BuildingNumber == currentbuildingnumber) {

    // Check if an existing view is being reused, otherwise inflate the view
    if (v == null) {
        v = LayoutInflater.from(getContext()).inflate(R.layout.project_actvitiy_list, parent, false);
    }

    // Get the {@link Word} object located at this position in the list
    currentActivity = getItem(position);

        TextView Act_ID = (TextView) v.findViewById(R.id.Act_ID);
        TextView Act_Name = (TextView) v.findViewById(R.id.Act_Name);
        TextView Act_Start = (TextView) v.findViewById(R.id.Act_Start);
        TextView Act_Prog = (TextView) v.findViewById(R.id.Act_Prog);
        TextView Act_Finish = (TextView) v.findViewById(R.id.Act_Finish);
        TextView Act_Note = (TextView) v.findViewById(R.id.Act_Note);

        Act_ID.setText(String.valueOf(currentActivity.getActivityID()));
        Act_Name.setText(String.valueOf(currentActivity.getActivityName()));
        Act_Start.setText(String.valueOf(currentActivity.getActualStart()));
        Act_Prog.setText(String.valueOf(currentActivity.getActivityProgress()));
        Act_Finish.setText(String.valueOf(currentActivity.getActualFinish()));
        Act_Note.setText(String.valueOf(currentActivity.getNotes()));

        Log.v("E1", "Activity ID is " + currentActivity.getActivityID());
        Log.v("E1", "Activity Name is " + currentActivity.getActivityName());
        Log.v("E1", "Activity Actual Start is " + currentActivity.getActualStart());
        Log.v("E1", "Activity Progress is " + currentActivity.getActivityProgress());
        Log.v("E1", "Activity Actual Finish is " + currentActivity.getActualFinish());
        Log.v("E1", "Activity Notes is " + currentActivity.getNotes());

}
    return v;
}
}

故障日志

代码语言：javascript
复制
--------- beginning of crash
08-07 19:59:21.764 14227-14227/com.example.mustafa.progressupdate E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.mustafa.progressupdate, PID: 14227
    java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getImportantForAccessibility()' on a null object reference
        at android.widget.AbsListView.obtainView(AbsListView.java:2379)
        at android.widget.ListView.makeAndAddView(ListView.java:1970)
        at android.widget.ListView.fillDown(ListView.java:704)
        at android.widget.ListView.fillFromTop(ListView.java:765)
        at android.widget.ListView.layoutChildren(ListView.java:1744)
        at android.widget.AbsListView.onLayout(AbsListView.java:2161)
        at android.view.View.layout(View.java:17523)
        at android.view.ViewGroup.layout(ViewGroup.java:5612)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at android.view.View.layout(View.java:17523)
        at android.view.ViewGroup.layout(ViewGroup.java:5612)
        at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:443)
        at android.view.View.layout(View.java:17523)
        at android.view.ViewGroup.layout(ViewGroup.java:5612)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at android.view.View.layout(View.java:17523)
        at android.view.ViewGroup.layout(ViewGroup.java:5612)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)
        at android.view.View.layout(View.java:17523)
        at android.view.ViewGroup.layout(ViewGroup.java:5612)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at com.android.internal.policy.DecorView.onLayout(DecorView.java:724)
        at android.view.View.layout(View.java:17523)
        at android.view.ViewGroup.layout(ViewGroup.java:5612)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2342)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2069)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1246)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6301)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:871)
        at android.view.Choreographer.doCallbacks(Choreographer.java:683)
        at android.view.Choreographer.doFrame(Choreographer.java:619)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:857)
        at android.os.Handler.handleCallback(Handler.java:751)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6077)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
08-07 19:59:21.765 1660-2992/system_process W/ActivityManager:   Force finishing activity com.example.mustafa.progressupdate/.E1
08-07 19:59:21.767 1785-2008/com.android.systemui D/EGL_emulation: eglMakeCurrent: 0xa0c38200: ver 3 1 (tinfo 0xa0c7f460)
08-07 19:59:21.772 1660-2992/system_process W/ActivityManager:   Force finishing activity com.example.mustafa.progressupdate/.SoleyaProjectSchedule
08-07 19:59:21.790 1660-1683/system_process I/WindowManager: Screen frozen for +190ms due to Window{36e1b87 u0 NavigationBar}
08-07 19:59:21.819 1785-2008/com.android.systemui D/EGL_emulation: eglMakeCurrent: 0xa0c38200: ver 3 1 (tinfo 0xa0c7f460)
08-07 19:59:21.832 1785-2008/com.android.systemui D/EGL_emulation: eglMakeCurrent: 0xa0c38200: ver 3 1 (tinfo 0xa0c7f460)
08-07 19:59:21.844 1660-1729/system_process I/OpenGLRenderer: Initialized EGL, version 1.4
08-07 19:59:21.844 1660-1729/system_process D/OpenGLRenderer: Swap behavior 1
08-07 19:59:21.845 1660-1729/system_process W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
08-07 19:59:21.845 1660-1729/system_process D/OpenGLRenderer: Swap behavior 0
08-07 19:59:21.848 1660-1729/system_process D/EGL_emulation: eglCreateContext: 0x92fa0300: maj 3 min 1 rcv 4
08-07 19:59:21.856 1660-1729/system_process D/EGL_emulation: eglMakeCurrent: 0x92fa0300: ver 3 1 (tinfo 0x9257e590)
08-07 19:59:21.859 1660-1729/system_process E/eglCodecCommon: glUtilsParamSize: unknow param 0x000082da
    glUtilsParamSize: unknow param 0x00008cdf
08-07 19:59:21.860 1660-1729/system_process E/eglCodecCommon: glUtilsParamSize: unknow param 0x00008824
08-07 19:59:21.867 1660-1729/system_process D/EGL_emulation: eglMakeCurrent: 0x92fa0300: ver 3 1 (tinfo 0x9257e590)
08-07 19:59:22.274 1660-1676/system_process W/ActivityManager: Activity pause timeout for ActivityRecord{96f635b u0 com.example.mustafa.progressupdate/.E1 t153 f}
08-07 19:59:24.800 1399-1422/? W/audio_hw_generic: Not supplying enough data to HAL, expected position 14558875 , only wrote 14290560
08-07 19:59:27.831 1660-1683/system_process I/art: Starting a blocking GC Explicit
08-07 19:59:27.857 1660-1683/system_process I/art: Explicit concurrent mark sweep GC freed 20596(1621KB) AllocSpace objects, 6(120KB) LOS objects, 26% free, 11MB/15MB, paused 846us total 26.282ms
08-07 19:59:30.905 1660-1739/system_process I/WifiConnectivityManager: start a single scan from watchdogHandler
    scheduleWatchdogTimer
08-07 19:59:31.600 1660-1676/system_process W/ActivityManager: Launch timeout has expired, giving up wake lock!
08-07 19:59:31.777 1660-1676/system_process W/ActivityManager: Activity destroy timeout for ActivityRecord{52aa486 u0 com.example.mustafa.progressupdate/.SoleyaProjectSchedule t153 f}
08-07 20:00:01.040 1785-2008/com.android.systemui D/EGL_emulation: eglMakeCurrent: 0xa0c38200: ver 3 1 (tinfo 0xa0c7f460)
'
java
android
EN

回答 1

Stack Overflow用户

回答已采纳

发布于 2018-08-08 01:54:29

==测试引用是否相等(无论它们是不是同一个对象)。

.equals()测试值是否相等(它们在逻辑上是否“相等”)。

more info

将==更改为.equals

票数 0
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/51732653

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