Java Android-空对象引用错误
这里有一些Android代码,它给了我一个空对象引用错误。不知道为什么会这样,但是我发现这与setStep()方法有关。不确定导致此错误的原因,但以下是我在logcat中得到的信息:Java Android-空对象引用错误,java,android,android-layout,Java,Android,Android Layout,这里有一些Android代码,它给了我一个空对象引用错误。不知道为什么会这样,但是我发现这与setStep()方法有关。不确定导致此错误的原因,但以下是我在logcat中得到的信息: 02-26 23:00:14.081 24821-24821/com.android.usagemonitor E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.android.usagemonitor, PID: 24821 java.lang.Runti
02-26 23:00:14.081 24821-24821/com.android.usagemonitor E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.android.usagemonitor, PID: 24821
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.usagemonitor/com.android.usemoncore.Activities.TypeActivities.NetActivity}: android.view.InflateException: Binary XML file line #7: Binary XML file line #7: Error inflating class com.android.usemoncore.Views.TypeLinearLayouts.NetLinearLayout
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3254)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: android.view.InflateException: Binary XML file line #7: Binary XML file line #7: Error inflating class com.android.usemoncore.Views.TypeLinearLayouts.NetLinearLayout
at android.view.LayoutInflater.inflate(LayoutInflater.java:551)
at android.view.LayoutInflater.inflate(LayoutInflater.java:429)
at android.view.LayoutInflater.inflate(LayoutInflater.java:380)
at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:474)
at android.app.Activity.setContentView(Activity.java:2387)
at com.android.usemoncore.Activities.TypeActivities.NetActivity.onCreate(NetActivity.java:12)
at android.app.Activity.performCreate(Activity.java:6876)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1135)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3207)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: android.view.InflateException: Binary XML file line #7: Error inflating class com.android.usemoncore.Views.TypeLinearLayouts.NetLinearLayout
at android.view.LayoutInflater.createView(LayoutInflater.java:657)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:776)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:716)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:847)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:810)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:855)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:810)
at android.view.LayoutInflater.inflate(LayoutInflater.java:527)
at android.view.LayoutInflater.inflate(LayoutInflater.java:429)
at android.view.LayoutInflater.inflate(LayoutInflater.java:380)
at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:474)
at android.app.Activity.setContentView(Activity.java:2387)
at com.android.usemoncore.Activities.TypeActivities.NetActivity.onCreate(NetActivity.java:12)
at android.app.Activity.performCreate(Activity.java:6876)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1135)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3207)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Constructor.newInstance(Native Method)
at android.view.LayoutInflater.createView(LayoutInflater.java:631)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:776)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:716)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:847)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:810)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:855)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:810)
at android.view.LayoutInflater.inflate(LayoutInflater.java:527)
at android.view.LayoutInflater.inflate(LayoutInflater.java:429)
at android.view.LayoutInflater.inflate(LayoutInflater.java:380)
at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:474)
at android.app.Activity.setContentView(Activity.java:2387)
at com.android.usemoncore.Activities.TypeActivities.NetActivity.onCreate(NetActivity.java:12)
at android.app.Activity.performCreate(Activity.java:6876)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1135)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3207)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.android.usemoncore.Views.GraphView.setStep(float)' on a null object reference
at com.android.usemoncore.Views.TypeLinearLayouts.NetLinearLayout.<init>(NetLinearLayout.java:22)
at java.lang.reflect.Constructor.newInstance(Native Method)
at android.view.LayoutInflater.createView(LayoutInflater.java:631)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:776)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:716)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:847)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:810)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:855)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:810)
at android.view.LayoutInflater.inflate(LayoutInflater.java:527)
at android.view.LayoutInflater.inflate(LayoutInflater.java:429)
at android.view.LayoutInflater.inflate(LayoutInflater.java:380)
at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:474)
at android.app.Activity.setContentView(Activity.java:2387)
at com.android.usemoncore.Activities.TypeActivities.NetActivity.onCreate(NetActivity.java:12)
at android.app.Activity.performCreate(Activity.java:6876)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1135)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3207)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
以下是linear_net.xml的代码:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android" xmlns:custom="http://schemas.android.com/apk/res-auto">
<com.android.usemoncore.Views.GraphView android:id="@+id/upgraph" android:layout_width="fill_parent" android:layout_height="60.0dip" android:layout_weight="1.0" custom:hlines_to_show="2" custom:vlines_to_show="2" custom:fixed_step="3" custom:vertical_top="true" custom:graphdatatype="netup" />
<com.android.usemoncore.Views.GraphView android:id="@+id/downgraph" android:layout_width="fill_parent" android:layout_height="60.0dip" android:layout_weight="1.0" custom:x_reversed="true" custom:hlines_to_show="2" custom:vlines_to_show="2" custom:fixed_step="3" custom:graphdatatype="netdown" />
此错误发生在上述代码的两个位置。造成这种情况的原因是什么?任何帮助都将不胜感激。我认为问题在于XML和代码之间存在某种不匹配。我希望有一行或两行:
downview = (GraphView) findViewById(R.id.downgraph);
upview = (GraphView) findViewById(R.id.upgraph);
正在返回null而不是视图。您可以添加调试来确认这一点。我认为原因是在这些调用时布局没有膨胀。也许你只需要先打个充气电话
所谓不匹配,我的意思是代码只希望获取ID,但没有获取ID,因此上下文有问题。看看这个问题在过去发生的方式。但我最近遇到的一个问题是,试图查找与setContentView()加载的文件不同的文件中的id。帮我找到了它。这是什么?这一步
this.upview.setStep(this.step);
downview = (GraphView) findViewById(R.id.downgraph);
upview = (GraphView) findViewById(R.id.upgraph);