android ClassCastException 类型转换错误

1.类型转换错误

03-09 09:45:01.884: E/AndroidRuntime(1847): FATAL EXCEPTION: main

03-09 09:45:01.884: E/AndroidRuntime(1847): Process: com.example.zhihudemo, PID: 1847

03-09 09:45:01.884: E/AndroidRuntime(1847): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.zhihudemo/com.example.zhihudemo.MainActivity}: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.ImageView

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2219)

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2269)

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.app.ActivityThread.access$800(ActivityThread.java:135)

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.os.Handler.dispatchMessage(Handler.java:102)

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.os.Looper.loop(Looper.java:136)

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.app.ActivityThread.main(ActivityThread.java:5045)

03-09 09:45:01.884: E/AndroidRuntime(1847): at java.lang.reflect.Method.invokeNative(Native Method)

03-09 09:45:01.884: E/AndroidRuntime(1847): at java.lang.reflect.Method.invoke(Method.java:515)

03-09 09:45:01.884: E/AndroidRuntime(1847): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)

03-09 09:45:01.884: E/AndroidRuntime(1847): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)

03-09 09:45:01.884: E/AndroidRuntime(1847): at dalvik.system.NativeStart.main(Native Method)

03-09 09:45:01.884: E/AndroidRuntime(1847): Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.ImageView

03-09 09:45:01.884: E/AndroidRuntime(1847): at com.example.zhihudemo.MainActivity.onCreate(MainActivity.java:40)

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.app.Activity.performCreate(Activity.java:5231)

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)

03-09 09:45:01.884: E/AndroidRuntime(1847): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2163)

03-09 09:45:01.884: E/AndroidRuntime(1847): ... 11 more

2.博主出错，是因为在调整 xml 布局的时候 没有 clean 项目，导致 bin 文件没有真正修改，所以现在 ImageView 的位置被认为还是 ViewPager 所以，出现类型转换错误

下面上 原布局 和 改动后的布局

原先是：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

tools:context="com.example.zhihudemo.MainActivity" >

<LinearLayout

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentBottom="true"

android:layout_centerInParent="true"

android:layout_marginBottom="50dp"

android:orientation="vertical" >

<LinearLayout

android:layout_width="wrap_content"

android:layout_height="wrap_content" >

<TextView

android:id="@+id/textView1"

android:layout_width="wrap_content"

android:layout_height="50dp"

android:layout_weight="1"

android:background="#999999"

android:gravity="center"

android:text="页面1"

android:textColor="#222222" />

<TextView

android:id="@+id/textView2"

android:layout_width="wrap_content"

android:layout_height="50dp"

android:layout_weight="1"

android:background="#999999"

android:gravity="center"

android:text="页面2"

android:textColor="#222222" />

<TextView

android:id="@+id/textView3"

android:layout_width="wrap_content"

android:layout_height="50dp"

android:layout_weight="1"

android:background="#999999"

android:gravity="center"

android:text="页面3"

android:textColor="#222222" />

</LinearLayout>

<ImageView

android:id="@+id/cursor"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:scaleType="matrix"

android:src="@drawable/cursor" />

</LinearLayout>

<android.support.v4.view.ViewPager

android:id="@+id/viewPager"

android:layout_width="fill_parent"

android:layout_height="wrap_content" />

</RelativeLayout>

改动后：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

tools:context="com.example.zhihudemo.MainActivity" >

<android.support.v4.view.ViewPager

android:id="@+id/viewPager"

android:layout_width="fill_parent"

android:layout_height="wrap_content" />

<LinearLayout

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentBottom="true"

android:layout_centerInParent="true"

android:layout_marginBottom="50dp"

android:orientation="vertical" >

<LinearLayout

android:layout_width="wrap_content"

android:layout_height="wrap_content" >

<TextView

android:id="@+id/textView1"

android:layout_width="wrap_content"

android:layout_height="50dp"

android:layout_weight="1"

android:background="#999999"

android:gravity="center"

android:text="页面1"

android:textColor="#222222" />

<TextView

android:id="@+id/textView2"

android:layout_width="wrap_content"

android:layout_height="50dp"

android:layout_weight="1"

android:background="#999999"

android:gravity="center"

android:text="页面2"

android:textColor="#222222" />

<TextView

android:id="@+id/textView3"

android:layout_width="wrap_content"

android:layout_height="50dp"

android:layout_weight="1"

android:background="#999999"

android:gravity="center"

android:text="页面3"

android:textColor="#222222" />

</LinearLayout>

<ImageView

android:id="@+id/cursor"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:scaleType="matrix"

android:src="@drawable/cursor" />

</LinearLayout>

</RelativeLayout>

解释：

其实 bin 文件已经编译好了，调换位置后由于改动较少，所以 xml 布局的改动并没有真正写入改动后的 bin 文件中，这是需要 clean 这个项目，重新编译即可