java.lang.ClassCastException: android.widget.LinearLayout 不能转换为 android.widget.ListView
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java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ListView
提问by Jagatjeet
Not sure why I am getting a ClassCastException in the code below. Changing ListActivity to Activity corrects the error but I want ListActivity as this is a part of the bigger code I am trying to build. Any help will be appreciated. Thanks
不知道为什么我在下面的代码中收到 ClassCastException。将 ListActivity 更改为 Activity 可以纠正错误，但我想要 ListActivity，因为这是我尝试构建的更大代码的一部分。任何帮助将不胜感激。谢谢
MainActivity.java
主活动.java
package com.example.debug;
import android.app.ListActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends ListActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
activity_main.xml:
活动_main.xml：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<!-- Name Label -->
<TextView
android:id="@+id/vehicleType"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#43bd00"
android:textSize="16sp"
android:textStyle="bold"
android:paddingTop="6dip"
android:text="Mobile1"
android:paddingBottom="2dip" />
<!-- Description Label -->
<TextView
android:id="@+id/vehicleColor"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#acacac"
android:text="Mobile2"
android:paddingBottom="2dip" />
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<!-- Cost Label -->
<TextView
android:id="@+id/fuel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#000000"
android:gravity="left"
android:textStyle="bold"
android:text="Mobile3" />
<!-- Price Label -->
<TextView
android:id="@+id/treadType"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#acacac"
android:text="Mobile4"
android:paddingBottom="2dip" />
</LinearLayout>
</LinearLayout>
<ListView
android:id="@android:id/list"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
</LinearLayout>
Stacktrace
堆栈跟踪
FATAL EXCEPTION: main
Process: com.example.debug, PID: 1370
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.debug/com.example.debug.MainActivity}: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ListView
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access0(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ListView
at android.app.ListActivity.onContentChanged(ListActivity.java:241)
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:293)
at android.app.Activity.setContentView(Activity.java:1929)
at com.example.debug.MainActivity.onCreate(MainActivity.java:14)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
... 11 more
回答by Blackbelt
your problem is with the root of your layout
你的问题是布局的根源
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
you give it the android:id="@android:id/list"the id the android reserves for the ListViewwidget. Change it in something else. E.g
你给它 android:id="@android:id/list"android 为ListView小部件保留的 id 。换个别的吧。例如
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/my_linear_layout"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
回答by Shivam Verma
In a ListActivity android looks for the widget with android:id="@android:id/list"and expects a ListView but in your case it finds the root LinearLayout and tries to cast it to a ListView hence the exception :
在 ListActivity android 中寻找带有android:id="@android:id/list"ListView的小部件， 但在您的情况下，它找到根 LinearLayout 并尝试将其转换为 ListView 因此异常：
Caused by: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ListView
To solve it, you just need to provide a different id as mentioned by Blackbelt.
要解决它，您只需要提供 Blackbelt 提到的不同 id。
回答by Akash
Your linear layout id should be as follows
您的线性布局 ID 应如下所示
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/my_linear_layout"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
回答by Dhiraj Singh
The solution of this error is LinearLayout expects ID attribute.
这个错误的解决方法是 LinearLayout 需要 ID 属性。
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/layout_container2"
android:layout_width="match_parent"
android:layout_height="match_parent">
<include
android:id="@+id/toolbar_noaction"
layout="@layout/toolbar"/>
</LinearLayout>
回答by Yuliia Ashomok
Find all usages of problematic id.
In IDEA IDE You can press Ctrl and click on your id for getting all usages.
查找有问题的 id 的所有用法。
在 IDEA IDE 中，您可以按 Ctrl 并单击您的 ID 以获取所有用法。
Note: It must be only one item with this id.
注意：它必须只有一个具有此 id 的项目。
回答by zeusboy
This problem can occur when we have a container in so many case a LinearLayout without id declared, you must put an android:id="@+id/layout_container" in your LinearLayout at the second level
当我们有一个容器时，可能会发生这个问题，在很多情况下，一个 LinearLayout 没有声明 id，你必须在你的 LinearLayout 的第二级放置一个 android:id="@+id/layout_container"
