这是 fragment 代码。
我正在尝试在内部创建一个按钮,但我不断收到错误。
public static class PlaceholderFragment extends Fragment {
Button startButton;
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView;
rootView = inflater.inflate(R.layout.fragment_main, container, false);
startButton = (Button) rootView.findViewById(R.id.enter);
startButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
startActivity(new Intent("com.appname.STUFF"));
}
});
return rootView;
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
}
}
这是我不断收到的错误。我不知道为什么,我尝试在很多地方这样做,但仍然收到此错误。
03-20 20:27:21.093: E/AndroidRuntime(27201): FATAL EXCEPTION: main
03-20 20:27:21.093: E/AndroidRuntime(27201): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.appname/com.appname.MainActivity}: java.lang.ClassCastException: android.widget.Button
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.os.Handler.dispatchMessage(Handler.java:99)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.os.Looper.loop(Looper.java:130)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.app.ActivityThread.main(ActivityThread.java:3691)
03-20 20:27:21.093: E/AndroidRuntime(27201): at java.lang.reflect.Method.invokeNative(Native Method)
03-20 20:27:21.093: E/AndroidRuntime(27201): at java.lang.reflect.Method.invoke(Method.java:507)
03-20 20:27:21.093: E/AndroidRuntime(27201): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:912)
03-20 20:27:21.093: E/AndroidRuntime(27201): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:670)
03-20 20:27:21.093: E/AndroidRuntime(27201): at dalvik.system.NativeStart.main(Native Method)
03-20 20:27:21.093: E/AndroidRuntime(27201): Caused by: java.lang.ClassCastException: android.widget.Button
03-20 20:27:21.093: E/AndroidRuntime(27201): at com.appname.MainActivity$PlaceholderFragment.onCreateView(MainActivity.java:179)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:928)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1105)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1468)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:570)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1132)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.app.Activity.performStart(Activity.java:3833)
03-20 20:27:21.093: E/AndroidRuntime(27201): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1624)
03-20 20:27:21.093: E/AndroidRuntime(27201): ... 11 more
这是 XML
<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"
android:background="@drawable/main"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.appname.MainActivity$PlaceholderFragment" >
<Button
android:id="@+id/enter"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="192dp"
android:text="Enter" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:text="TITLE"
android:textSize="50sp" />
</RelativeLayout>
最佳答案
检查您的导入:
import android.widget.Button;
清理并重建 (显然,这对您没有任何改变)。
删除并手动重建您的 xml Button,它会自动重建您的 R 文件。
不确定,但也许相关。将您的 Intent 方法更改为:
Intent i = new Intent();
i.setClassName("com.appname.ACTIVITY", "com.appname.STUFF");
getActivity().startActivity(i);
或者使用不带PackageName的ClassName:
getActivity().startActivity(new Intent(getActivity(), StuffActivity.class);
还要确保导入正确的类名称。
如果这不起作用,请将您的 onClickListener
更改为 onClick 方法,例如:
// in your xml Button
android:onClick="launchActivity"
// in your Fragment
public void launchActivity(View view) {
getActivity().startActivity(new Intent(getActivity(), StuffActivity.class);
}
您还可以从 Fragment
调用 FragmentActivity
的方法,如下所示:
// Fragment: onClickListener
startButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
((Activity) getActivity()).launchActivity();
}
}
// FragmentActivity: launchActivity method
public void launchActivity() {
startActivity(new Intent(Activity.this, StuffActivity.class));
}
希望你能实现你想要的。
关于java - Android:在 fragment 上创建按钮时出现 classcastException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22547932/