在 JAVA ANDROID SDK 中动态创建按钮和文本

【问题标题】：Create buttons and text dynamically in JAVA ANDROID SDK在 JAVA ANDROID SDK 中动态创建按钮和文本
【发布时间】：2014-04-17 20:05:30
【问题描述】：

我在ANDROID SDK 中有一个错误，这个简单的代码：

LinearLayout layout1 = (LinearLayout) findViewById(R.id.layout1);

Button button1 = new Button(this);
button1.setText(R.string.button_misto);

TextView textView1 = new TextView(this);
textView1.setText("Something cool");

layout1.addView(textView1);

我只想在运行时创建对象。

我在这一行收到java.lang.NullPointerException

layout1.addView(textView1);

或

layout1.addView(button1);

这就像button1 和textView1 是NULL。我做错了什么？

这是错误：

04-17 22:52:18.046: E/FragmentManager(23649): No view found for id 0x7f05003c (com.example.app2:id/container) for fragment PlaceholderFragment{4057ebf8 #0 id=0x7f05003c}
04-17 22:52:18.046: E/FragmentManager(23649): Activity state:
04-17 22:52:18.046: D/FragmentManager(23649):   Local FragmentActivity 40574780 State:
04-17 22:52:18.046: D/FragmentManager(23649):     mCreated=truemResumed=false mStopped=false mReallyStopped=false
04-17 22:52:18.046: D/FragmentManager(23649):     mLoadersStarted=false
04-17 22:52:18.046: D/FragmentManager(23649):   Active Fragments in 405748c8:
04-17 22:52:18.046: D/FragmentManager(23649):     #0: PlaceholderFragment{4057ebf8 #0 id=0x7f05003c}
04-17 22:52:18.046: D/FragmentManager(23649):       mFragmentId=#7f05003c mContainerId=#7f05003c mTag=null
04-17 22:52:18.054: D/FragmentManager(23649):       mState=0 mIndex=0 mWho=android:fragment:0 mBackStackNesting=0
04-17 22:52:18.054: D/FragmentManager(23649):       mAdded=true mRemoving=false mResumed=false mFromLayout=false mInLayout=false
04-17 22:52:18.054: D/FragmentManager(23649):       mHidden=false mDetached=false mMenuVisible=true mHasMenu=false
04-17 22:52:18.054: D/FragmentManager(23649):       mRetainInstance=false mRetaining=false mUserVisibleHint=true
04-17 22:52:18.062: D/FragmentManager(23649):       mFragmentManager=FragmentManager{405748c8 in ForthActivity{40574780}}
04-17 22:52:18.062: D/FragmentManager(23649):       mActivity=com.example.app2.ForthActivity@40574780
04-17 22:52:18.062: D/FragmentManager(23649):   Added Fragments:
04-17 22:52:18.062: D/FragmentManager(23649):     #0: PlaceholderFragment{4057ebf8 #0 id=0x7f05003c}
04-17 22:52:18.062: D/FragmentManager(23649):   FragmentManager misc state:
04-17 22:52:18.062: D/FragmentManager(23649):     mActivity=com.example.app2.ForthActivity@40574780
04-17 22:52:18.062: D/FragmentManager(23649):     mContainer=android.support.v4.app.FragmentActivity$2@40574940
04-17 22:52:18.062: D/FragmentManager(23649):     mCurState=2 mStateSaved=false mDestroyed=false
04-17 22:52:18.070: D/FragmentManager(23649):   View Hierarchy:
04-17 22:52:18.070: D/FragmentManager(23649):     com.android.internal.policy.impl.PhoneWindow$DecorView{405755e0 V.E..... ... 0,0-0,0}
04-17 22:52:18.070: D/FragmentManager(23649):       android.widget.FrameLayout{405759b8 V.E..... ... 0,0-0,0}
04-17 22:52:18.070: D/FragmentManager(23649):         android.widget.LinearLayout{405762f0 V.E..... ... 0,0-0,0}
04-17 22:52:18.070: D/FragmentManager(23649):           android.support.v7.internal.widget.ActionBarContainer{40576710 V.ED.... ... 0,0-0,0 #7f05001b app:id/action_bar_container}
04-17 22:52:18.070: D/FragmentManager(23649):             android.support.v7.internal.widget.ActionBarView{40576e70 V.E..... ... 0,0-0,0 #7f05001c app:id/action_bar}
04-17 22:52:18.070: D/FragmentManager(23649):               android.widget.LinearLayout{4057b168 G.....C. ... 0,0-0,0}
04-17 22:52:18.070: D/FragmentManager(23649):                 android.widget.ImageView{4057bab8 G.ED.... ... 0,0-0,0 #7f050021 app:id/up}
04-17 22:52:18.078: D/FragmentManager(23649):                 android.widget.LinearLayout{4057bcf0 V.E..... ... 0,0-0,0}
04-17 22:52:18.078: D/FragmentManager(23649):                   android.widget.TextView{4057bf58 V.ED.... ... 0,0-0,0 #7f050022 app:id/action_bar_title}
04-17 22:52:18.078: D/FragmentManager(23649):                   android.widget.TextView{4057cb88 G.ED.... ... 0,0-0,0 #7f050023 app:id/action_bar_subtitle}
04-17 22:52:18.078: D/FragmentManager(23649):               android.support.v7.internal.widget.ActionBarView$HomeView{40577fa8 VFE...C. ... 0,0-0,0}
04-17 22:52:18.078: D/FragmentManager(23649):                 android.widget.ImageView{40579d18 G.ED.... ... 0,0-0,0 #7f050021 app:id/up}
04-17 22:52:18.078: D/FragmentManager(23649):                 android.widget.ImageView{4057a0e0 V.ED.... ... 0,0-0,0 #7f050014 app:id/home}
04-17 22:52:18.078: D/FragmentManager(23649):             android.support.v7.internal.widget.ActionBarContextView{4057d170 G.E..... ... 0,0-0,0 #7f05001d app:id/action_context_bar}
04-17 22:52:18.078: D/FragmentManager(23649):           android.widget.FrameLayout{4057d840 V.E..... ... 0,0-0,0 #1020002 android:id/content}
04-17 22:52:18.085: D/FragmentManager(23649):             android.widget.LinearLayout{4057ed38 V.E..... ... 0,0-0,0}
04-17 22:52:18.085: D/FragmentManager(23649):               android.widget.TextView{4057efe0 V.ED.... ... 0,0-0,0}
04-17 22:52:18.085: D/FragmentManager(23649):           android.support.v7.internal.widget.ActionBarContainer{4057daa8 G.ED.... ... 0,0-0,0 #7f05001e app:id/split_action_bar}
04-17 22:52:18.085: D/AndroidRuntime(23649): Shutting down VM
04-17 22:52:18.085: W/dalvikvm(23649): threadid=1: thread exiting with uncaught exception (group=0x40018578)
04-17 22:52:18.093: E/AndroidRuntime(23649): FATAL EXCEPTION: main
04-17 22:52:18.093: E/AndroidRuntime(23649): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.app2/com.example.app2.ForthActivity}: java.lang.IllegalArgumentException: No view found for id 0x7f05003c (com.example.app2:id/container) for fragment PlaceholderFragment{4057ebf8 #0 id=0x7f05003c}
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.os.Looper.loop(Looper.java:130)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.app.ActivityThread.main(ActivityThread.java:3687)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at java.lang.reflect.Method.invokeNative(Native Method)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at java.lang.reflect.Method.invoke(Method.java:507)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at dalvik.system.NativeStart.main(Native Method)
04-17 22:52:18.093: E/AndroidRuntime(23649): Caused by: java.lang.IllegalArgumentException: No view found for id 0x7f05003c (com.example.app2:id/container) for fragment PlaceholderFragment{4057ebf8 #0 id=0x7f05003c}
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:919)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:570)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.app.Activity.performStart(Activity.java:3802)
04-17 22:52:18.093: E/AndroidRuntime(23649):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1624)
04-17 22:52:18.093: E/AndroidRuntime(23649):    ... 11 more
04-17 22:53:37.367: W/KeyCharacterMap(23700): Can't open keycharmap file
04-17 22:53:37.367: W/KeyCharacterMap(23700): Error loading keycharmap file
04-17 22:53:37.367: W/KeyCharacterMap(23700): Using default keymap
04-17 22:53:52.750: W/KeyCharacterMap(23771): Can't open keycharmap file
04-17 22:53:52.750: W/KeyCharacterMap(23771): Error loading keycharmap file
04-17 22:53:52.750: W/KeyCharacterMap(23771): Using default keymap
04-17 22:55:58.898: W/KeyCharacterMap(23953): Can't open keycharmap file
04-17 22:55:58.898: W/KeyCharacterMap(23953): Error loading keycharmap file
04-17 22:55:58.898: W/KeyCharacterMap(23953): Using default keymap
04-17 22:56:00.164: D/dalvikvm(23953): GC_CONCURRENT freed 233K, 46% free 3170K/5831K, external 922K/1036K, paused 5ms+5ms
04-17 22:56:00.195: D/dalvikvm(23953): GC_FOR_MALLOC freed 54K, 47% free 3180K/5959K, external 922K/1036K, paused 29ms
04-17 22:56:00.234: D/dalvikvm(23953): GC_FOR_MALLOC freed 3K, 47% free 3305K/6151K, external 922K/1036K, paused 28ms
04-17 22:56:00.281: D/dalvikvm(23953): GC_FOR_MALLOC freed 7K, 47% free 3297K/6151K, external 922K/1036K, paused 32ms
04-17 22:56:00.328: D/dalvikvm(23953): GC_FOR_MALLOC freed 0K, 44% free 3809K/6727K, external 922K/1036K, paused 28ms
04-17 22:56:00.445: D/dalvikvm(23953): GC_CONCURRENT freed 2K, 44% free 3822K/6727K, external 922K/1036K, paused 4ms+3ms
04-17 22:56:01.242: W/KeyCharacterMap(23953): Can't open keycharmap file
04-17 22:56:01.242: W/KeyCharacterMap(23953): Error loading keycharmap file
04-17 22:56:01.242: W/KeyCharacterMap(23953): Using default keymap
04-17 22:56:28.757: D/dalvikvm(24107): GC_FOR_MALLOC freed 157K, 45% free 3227K/5767K, external 922K/1036K, paused 93ms
04-17 22:56:28.859: D/dalvikvm(24107): GC_FOR_MALLOC freed 46K, 45% free 3308K/5959K, external 922K/1036K, paused 96ms
04-17 22:56:29.007: D/dalvikvm(24107): GC_FOR_MALLOC freed 3K, 42% free 3817K/6535K, external 922K/1036K, paused 126ms
04-17 22:56:29.132: D/dalvikvm(24107): GC_CONCURRENT freed 18K, 42% free 3807K/6535K, external 922K/1036K, paused 4ms+4ms
04-17 22:56:29.664: W/KeyCharacterMap(24107): Can't open keycharmap file
04-17 22:56:29.664: W/KeyCharacterMap(24107): Error loading keycharmap file
04-17 22:56:29.664: W/KeyCharacterMap(24107): Using default keymap
04-17 22:56:30.757: D/AndroidRuntime(24107): Shutting down VM
04-17 22:56:30.757: W/dalvikvm(24107): threadid=1: thread exiting with uncaught exception (group=0x40018578)
04-17 22:56:30.765: E/AndroidRuntime(24107): FATAL EXCEPTION: main
04-17 22:56:30.765: E/AndroidRuntime(24107): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.app2/com.example.app2.ForthActivity}: java.lang.NullPointerException
04-17 22:56:30.765: E/AndroidRuntime(24107):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at android.os.Looper.loop(Looper.java:130)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at android.app.ActivityThread.main(ActivityThread.java:3687)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at java.lang.reflect.Method.invokeNative(Native Method)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at java.lang.reflect.Method.invoke(Method.java:507)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at dalvik.system.NativeStart.main(Native Method)
04-17 22:56:30.765: E/AndroidRuntime(24107): Caused by: java.lang.NullPointerException
04-17 22:56:30.765: E/AndroidRuntime(24107):    at com.example.app2.ForthActivity.onCreate(ForthActivity.java:40)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-17 22:56:30.765: E/AndroidRuntime(24107):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
04-17 22:56:30.765: E/AndroidRuntime(24107):    ... 11 more

编辑

ForthActivity.java http://pastebin.com/TDbHikXZ

activity_forth.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.app2.ForthActivity"
    tools:ignore="MergeRootFrame" />

fragment_forth.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" 
    android:id="@+id/layout1"
    >

</LinearLayout>

【问题讨论】：

  • 你确定layout1 不为空吗？
  • 我认为您使用的是PlaceholderFragment，您必须将此代码放入您的Fragment 方法onCreateView()
  • layout1 不为空，看下贴...，而且我没有用Fragment，只是一个简单的应用程序，我只是想做一个JSON登录...

标签： java android android-layout android-intent android-listview


【解决方案1】：

layout1 为 null，可能您没有使用 setContentView 行，或者您的布局中不存在此视图。

【讨论】：

  • 显示您设置布局的位置。如果您使用的是 Fragment，请展示您的 onCreateView 方法实现
  • 我不使用fragment，只是一个简单的应用，看这里i62.tinypic.com/2mzi80w.jpg
  • 您正在使用名为PlaceholderFragment的片段显示.java此片段方法的代码
  • 您正在使用Fragment 并且布局在片段中！请在使用前阅读一些关于片段的教程。您的代码应该在PlaceholderFragment 类代码中的onActivityCreated() 方法中
  • 我正在 lynda.com 上做教程，我是片段 i.stack.imgur.com/f04gn.png。
【解决方案2】：

这是因为您将内容视图设置为布局 activity_forth.xml 然后您通过 id (R.id.layout1) 调用查找视图，这不在此布局中。 您正在搜索当前布局中不存在的视图。

这应该让你开始 setContentView(R.layout.fragment_forth.xml); LinearLayout ll = () findViewById(R.id.layout1);

希望对你有帮助。

【讨论】：

    猜你喜欢
    • 1970-01-01
    • 1970-01-01
    • 1970-01-01
    • 1970-01-01
    • 2017-05-23
    • 1970-01-01
    • 1970-01-01
    • 1970-01-01
    • 1970-01-01
    相关资源
    最近更新 更多
    热门标签
    Java Python linux javascript Mysql C# Docker 算法 前端 SpringBoot Redis Vue spring 设计模式 .net core .net kubernetes c++ 数据库 数据结构 大数据 js 机器学习 微服务 Android Go 程序员 面试 JVM ASP.net core 云原生 人工智能 后端 PHP git CSS golang k8s Nginx Django mybatis 深度学习 多线程 React 架构 devops 爬虫 云计算 Spring Boot LeetCode