java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.gchat / com.example.gchat.HomeActivity}：java.lang.NullPointerException
我试图创建一个这样的菜单（灰色背景中的菜单） -
我使用LayoutInflator制作它。其代码如下 -
ImageView imgv1, imgv2;
TextView tv1, tv2, tv3;
private Animation down;
View child;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
imgv1 = (ImageView) findViewById(R.id.imageViewHA1);
imgv2 = (ImageView) findViewById(R.id.imageViewHA2);
tv1 = (TextView) findViewById(R.id.textViewMenu1);
tv2 = (TextView) findViewById(R.id.textViewMenu2);
tv3 = (TextView) findViewById(R.id.textViewMenu3);
down = AnimationUtils.loadAnimation(this, R.anim.slide_down);
imgv2.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
LinearLayout item = (LinearLayout) findViewById(R.id.linearLayout2);
if (child == null)
{
item.setAnimation(down);
down.start();
child = getLayoutInflater().inflate(R.layout.menu_layout, null);
item.addView(child);
} else
{
item.removeAllViews();
child = null;
}
}
});
tv3.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
System.exit(0);
}
});
}
R.layout.menu_layout代码 -
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/RelativeLayout1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical" >
<LinearLayout
android:id="@+id/menulayout1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@color/White"
android:orientation="vertical"
android:showDividers="middle" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="3dp"
android:layout_marginRight="3dp"
android:layout_marginTop="2dp"
android:background="@color/DimGray" >
<TextView
android:id="@+id/textViewMenu1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:paddingBottom="3dp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="3dp"
android:text="New Group"
android:textColor="@color/White"
android:textStyle="bold" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="3dp"
android:layout_marginRight="3dp"
android:layout_marginTop="2dp"
android:background="@color/DimGray" >
<TextView
android:id="@+id/textViewMenu2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:paddingBottom="3dp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="3dp"
android:text="Contacts"
android:textColor="@color/White"
android:textStyle="bold" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="3dp"
android:layout_marginRight="3dp"
android:layout_marginTop="2dp"
android:background="@color/DimGray"
android:orientation="vertical" >
<TextView
android:id="@+id/textViewMenu3"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:paddingBottom="3dp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="3dp"
android:text="Exit"
android:textColor="@color/White"
android:textStyle="bold" />
</LinearLayout>
</LinearLayout>
</RelativeLayout>
当我运行我的代码时，我得到了这个问题标题中的异常。 LogCat的详细信息在这里 -
09-18 22:06:50.369: E/AndroidRuntime(952): FATAL EXCEPTION: main
09-18 22:06:50.369: E/AndroidRuntime(952): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gchat/com.example.gchat.HomeActivity}: java.lang.NullPointerException
09-18 22:06:50.369: E/AndroidRuntime(952): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
09-18 22:06:50.369: E/AndroidRuntime(952): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-18 22:06:50.369: E/AndroidRuntime(952): at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-18 22:06:50.369: E/AndroidRuntime(952): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-18 22:06:50.369: E/AndroidRuntime(952): at android.os.Handler.dispatchMessage(Handler.java:99)
09-18 22:06:50.369: E/AndroidRuntime(952): at android.os.Looper.loop(Looper.java:137)
09-18 22:06:50.369: E/AndroidRuntime(952): at android.app.ActivityThread.main(ActivityThread.java:4745)
09-18 22:06:50.369: E/AndroidRuntime(952): at java.lang.reflect.Method.invokeNative(Native Method)
09-18 22:06:50.369: E/AndroidRuntime(952): at java.lang.reflect.Method.invoke(Method.java:511)
09-18 22:06:50.369: E/AndroidRuntime(952): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-18 22:06:50.369: E/AndroidRuntime(952): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-18 22:06:50.369: E/AndroidRuntime(952): at dalvik.system.NativeStart.main(Native Method)
09-18 22:06:50.369: E/AndroidRuntime(952): Caused by: java.lang.NullPointerException
09-18 22:06:50.369: E/AndroidRuntime(952): at com.example.gchat.HomeActivity.onCreate(HomeActivity.java:58)
09-18 22:06:50.369: E/AndroidRuntime(952): at android.app.Activity.performCreate(Activity.java:5008)
09-18 22:06:50.369: E/AndroidRuntime(952): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
09-18 22:06:50.369: E/AndroidRuntime(952): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
09-18 22:06:50.369: E/AndroidRuntime(952): ... 11 more
09-18 22:16:03.709: E/Trace(998): error opening trace file: No such file or directory (2)
09-18 22:16:04.238: D/AndroidRuntime(998): Shutting down VM
09-18 22:16:04.238: W/dalvikvm(998): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
09-18 22:16:04.248: E/AndroidRuntime(998): FATAL EXCEPTION: main
09-18 22:16:04.248: E/AndroidRuntime(998): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gchat/com.example.gchat.HomeActivity}: java.lang.ClassCastException: com.example.gchat.HomeActivity cannot be cast to android.view.View$OnClickListener
09-18 22:16:04.248: E/AndroidRuntime(998): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
09-18 22:16:04.248: E/AndroidRuntime(998): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-18 22:16:04.248: E/AndroidRuntime(998): at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-18 22:16:04.248: E/AndroidRuntime(998): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-18 22:16:04.248: E/AndroidRuntime(998): at android.os.Handler.dispatchMessage(Handler.java:99)
09-18 22:16:04.248: E/AndroidRuntime(998): at android.os.Looper.loop(Looper.java:137)
09-18 22:16:04.248: E/AndroidRuntime(998): at android.app.ActivityThread.main(ActivityThread.java:4745)
09-18 22:16:04.248: E/AndroidRuntime(998): at java.lang.reflect.Method.invokeNative(Native Method)
09-18 22:16:04.248: E/AndroidRuntime(998): at java.lang.reflect.Method.invoke(Method.java:511)
09-18 22:16:04.248: E/AndroidRuntime(998): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-18 22:16:04.248: E/AndroidRuntime(998): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-18 22:16:04.248: E/AndroidRuntime(998): at dalvik.system.NativeStart.main(Native Method)
09-18 22:16:04.248: E/AndroidRuntime(998): Caused by: java.lang.ClassCastException: com.example.gchat.HomeActivity cannot be cast to android.view.View$OnClickListener
09-18 22:16:04.248: E/AndroidRuntime(998): at com.example.gchat.HomeActivity.onCreate(HomeActivity.java:35)
09-18 22:16:04.248: E/AndroidRuntime(998): at android.app.Activity.performCreate(Activity.java:5008)
09-18 22:16:04.248: E/AndroidRuntime(998): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
09-18 22:16:04.248: E/AndroidRuntime(998): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
09-18 22:16:04.248: E/AndroidRuntime(998): ... 11 more
09-18 22:20:33.669: E/Trace(1046): error opening trace file: No such file or directory (2)
09-18 22:20:33.989: D/AndroidRuntime(1046): Shutting down VM
09-18 22:20:34.029: W/dalvikvm(1046): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
09-18 22:20:34.079: E/AndroidRuntime(1046): FATAL EXCEPTION: main
09-18 22:20:34.079: E/AndroidRuntime(1046): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gchat/com.example.gchat.HomeActivity}: java.lang.NullPointerException
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.os.Handler.dispatchMessage(Handler.java:99)
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.os.Looper.loop(Looper.java:137)
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.app.ActivityThread.main(ActivityThread.java:4745)
09-18 22:20:34.079: E/AndroidRuntime(1046): at java.lang.reflect.Method.invokeNative(Native Method)
09-18 22:20:34.079: E/AndroidRuntime(1046): at java.lang.reflect.Method.invoke(Method.java:511)
09-18 22:20:34.079: E/AndroidRuntime(1046): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-18 22:20:34.079: E/AndroidRuntime(1046): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-18 22:20:34.079: E/AndroidRuntime(1046): at dalvik.system.NativeStart.main(Native Method)
09-18 22:20:34.079: E/AndroidRuntime(1046): Caused by: java.lang.NullPointerException
09-18 22:20:34.079: E/AndroidRuntime(1046): at com.example.gchat.HomeActivity.onCreate(HomeActivity.java:58)
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.app.Activity.performCreate(Activity.java:5008)
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
09-18 22:20:34.079: E/AndroidRuntime(1046): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
09-18 22:20:34.079: E/AndroidRuntime(1046): ... 11 more
我在这里和谷歌搜索了很多，但是找不到任何有用的东西。如何更正此错误？
1 个答案:
答案 0 :(得分：2)
即使在给布局膨胀之前，您正在访问子视图，这是您获得的第一个原因NullPointerException
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gchat/com.example.gchat.HomeActivity}: java.lang.NullPointerException
首先对布局进行膨胀，然后使用该膨胀的布局参考访问其子视图。否则，系统将无法理解视图，您正在尝试使用，属于充气布局。
例如：
View view = getLayoutInflater().inflate(R.layout.menu_layout, null);
TextView tv1 = (TextView) view.findViewById(R.id.textViewMenu1);
<强>更新
您应该初始化TextViews充气布局，如下所示
if (child == null) {
item.setAnimation(down);
down.start();
child = getLayoutInflater().inflate(R.layout.menu_layout, null);
tv1 = (TextView) child.findViewById(R.id.textViewMenu1);
tv2 = (TextView) child.findViewById(R.id.textViewMenu2);
tv3 = (TextView) child.findViewById(R.id.textViewMenu3);
tv3.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
//you code
}
});
item.addView(child);
}
相关问题
- java.lang.RuntimeException：无法启动活动ComponentInfo java.lang.NullPointerException
- java.lang.RuntimeException：无法启动活动ComponentInfo：java.lang.NullPointerException
- java.lang.RuntimeException：无法启动活动ComponentInfo java.lang.NullPointerException
- Java.lang.runtimeexception无法启动活动componentinfo java.lang.nullpointerexception
- java.lang.RuntimeException：无法启动活动ComponentInfo {...}：java.lang.NullPointerException
- java.lang.RuntimeException：无法启动活动ComponentInfo {}：java.lang.NullPointerException
- java.lang.RuntimeException：无法启动活动ComponentInfo {....}：java.lang.NullPointerException
- java.lang.RuntimeException：无法启动活动ComponentInfo {..} java.lang.NullPointerException
- java.lang.RuntimeException：无法启动活动ComponentInfo {...}：java.lang.NullPointerException
- java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.namecardlistview.MainActivity}：java.lang.NullPointerException
最新问题
- 我写了这段代码，但我无法理解我的错误
- 我无法从一个代码实例的列表中删除 None 值，但我可以在另一个实例中。为什么它适用于一个细分市场而不适用于另一个细分市场？
- 是否有可能使 loadstring 不可能等于打印？卢阿
- java中的random.expovariate()
- Appscript 通过会议在 Google 日历中发送电子邮件和创建活动
- 为什么我的 Onclick 箭头功能在 React 中不起作用？
- 在此代码中是否有使用“this”的替代方法？
- 在 SQL Server 和 PostgreSQL 上查询，我如何从第一个表获得第二个表的可视化
- 每千个数字得到
- 更新了城市边界 KML 文件的来源？