带有android片段的java.lang.NullPointerException

概述我正在尝试在我的应用程序中实现Fragments.当我更改标签(我使用抽屉布局)时出现问题,我收到java.lang.NullPointerException错误.我测试了主要活动的代码并且运行顺利.唯一的问题是我在片段上应用它.这是代码：importandroid.app.Fragment;importandroid.os.Bundle;importandr

我正在尝试在我的应用程序中实现Fragments.当我更改标签(我使用抽屉布局)时出现问题,我收到java.lang.NullPointerException错误.我测试了主要活动的代码并且运行顺利.唯一的问题是我在片段上应用它.这是代码：

import androID.app.Fragment;import androID.os.Bundle;import androID.support.annotation.Nullable;import androID.vIEw.LayoutInflater;import androID.vIEw.VIEw;import androID.vIEw.VIEwGroup;import androID.Widget.*;public class FragW extends Fragment {    Spinner spinwatt ;    button calculate;    EditText wattEdit;    EditText costEdit;    TextVIEw resultText;    @Nullable    @OverrIDe    public VIEw onCreateVIEw(LayoutInflater inflater, VIEwGroup container, Bundle savedInstanceState) {        VIEw v = inflater.inflate(R.layout.fragw,container,false);        calculate = (button) getVIEw().findVIEwByID(R.ID.calculate);        wattEdit = (EditText) getVIEw().findVIEwByID(R.ID.wattEdit);        costEdit = (EditText) getVIEw().findVIEwByID(R.ID.costEdit);        calculate.setonClickListener(new VIEw.OnClickListener() {            @OverrIDe            public voID onClick(VIEw vIEw) {                float wattvar = float.parsefloat(wattEdit.getText().toString());                float costvar = float.parsefloat(costEdit.getText().toString());                if (spinwatt.getSelectedItem().toString().equals("µW"))                    wattvar = wattvar * (float) 0.000001;                else if (spinwatt.getSelectedItem().toString().equals("mW"))                    wattvar = wattvar * (float) 0.001;                else if (spinwatt.getSelectedItem().toString().equals("kW"))                    wattvar = wattvar * 1000;                String resultvar = float.toString(costvar * wattvar);                resultText.setText(resultvar);            }        });        spinwatt = (Spinner)getVIEw().findVIEwByID(R.ID.spinwatt);        ArrayAdapter<CharSequence> wattAdapter = ArrayAdapter.createFromresource(getActivity(),                R.array.wattArray, androID.R.layout.simple_spinner_item);        wattAdapter.setDropDownVIEwResource(androID.R.layout.simple_spinner_dropdown_item);        spinwatt.setAdapter(wattAdapter);        return v;    }

这是logCat

10-13 12:27:13.429    2563-2563/az.test2 D/gralloc_goldfish﹕ Emulator without GPU emulation detected.10-13 12:27:31.468    2563-2563/az.test2 D/AndroIDRuntime﹕ Shutting down VM10-13 12:27:31.468    2563-2563/az.test2 W/dalvikvm﹕ threadID=1: thread exiting with uncaught exception (group=0x409961f8)10-13 12:27:31.488    2563-2563/az.test2 E/AndroIDRuntime﹕ FATAL EXCEPTION: mainjava.lang.NullPointerException        at az.test2.FragW.onCreateVIEw(FragW.java:25)        at androID.app.FragmentManagerImpl.movetoState(FragmentManager.java:795)        at androID.app.FragmentManagerImpl.movetoState(FragmentManager.java:998)        at androID.app.BackStackRecord.run(BackStackRecord.java:622)        at androID.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1330)        at androID.app.FragmentManagerImpl.run(FragmentManager.java:417)        at androID.os.Handler.handleCallback(Handler.java:605)        at androID.os.Handler.dispatchMessage(Handler.java:92)        at androID.os.Looper.loop(Looper.java:137)        at androID.app.ActivityThread.main(ActivityThread.java:4340)        at java.lang.reflect.Method.invokeNative(Native Method)        at java.lang.reflect.Method.invoke(Method.java:511)        at com.androID.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)        at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:551)        at dalvik.system.NativeStart.main(Native Method)

第25行是：calculate =(button)getVIEw().findVIEwByID(R.ID.calculate);.但是,所有这样的行都会导致此错误(第25,26,27,55行).我还尝试用定义初始化变量(在第16行到第20行)我仍然得到了相同的错误.
请告诉我应该怎么做.

解决方法:

改变这一点

    calculate = (button) getVIEw().findVIEwByID(R.ID.calculate);    wattEdit = (EditText) getVIEw().findVIEwByID(R.ID.wattEdit);    costEdit = (EditText) getVIEw().findVIEwByID(R.ID.costEdit);

至

    calculate = (button) v.findVIEwByID(R.ID.calculate);    wattEdit = (EditText) v.findVIEwByID(R.ID.wattEdit);    costEdit = (EditText) v.findVIEwByID(R.ID.costEdit);

从Fragment中的膨胀视图初始化您的视图

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