底部工作表对话框片段不显示
底部工作表对话框片段不显示
提问于 2018-06-08 05:56:55
我创建了一个Modal Bottom Sheet片段，默认情况下有以下几行
/**
* <p>A fragment that shows a list of items as a modal bottom sheet.</p>
* <p>You can show this modal bottom sheet from your activity like this:</p>
* <pre>
* ShoppingCartListDialogFragment.newInstance(30).show(getSupportFragmentManager(), "dialog");
* </pre>
* <p>You activity (or fragment) needs to implement {@link ShoppingCartListDialogFragment.Listener}.</p>
*/然后在我的MainActivity.java上有一个onClick函数，如下所示：
public void showShoppingCart(View view) {
// Testing
ShoppingCartListDialogFragment.newInstance(30).show(getSupportFragmentManager(), "dialog");
}每当我单击应用程序崩溃的按钮时，我就会从片段的onAttach方法中得到一个错误
@Override
public void onAttach(Context context) {
super.onAttach(context);
final Fragment parent = getParentFragment();
if (parent != null) {
mListener = (Listener) parent;
} else {
mListener = (Listener) context; <-- Error on this line
}
}有人知道我错过了什么吗？我真的不明白最后一行的评论。我在哪里实现.Listener？
错误日志：
FATAL EXCEPTION: main
Process: com.example.johng.assosfood, PID: 28856
java.lang.ClassCastException: com.example.johng.assosfood.ProductsActivity cannot be cast to com.example.johng.assosfood.ShoppingCartListDialogFragment$Listener
at com.example.johng.assosfood.ShoppingCartListDialogFragment.onAttach(ShoppingCartListDialogFragment.java:59)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1367)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1754)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1822)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:797)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2591)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2378)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2333)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2240)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:703)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6682)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)回答 1
Stack Overflow用户
回答已采纳
发布于 2018-06-08 06:10:01
当我为片段设置侦听器时，我的onAttach()通常如下所示：
@Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof yourFragmentListener) {
mListener = (yourFragmentListener) context;
} else {
// Error Code
}
}这样，它只在附加到的活动实现其侦听器时才进行强制转换。如果您得到的是错误代码，则很可能没有在MainActivity中实现片段的侦听器。如下所示：
public class MainActivity extends Activity implements ShoppingCartListDialog.Listener {
// If it successfully implements, (you have all the methods
//defined in this class) then it is an instance of the listener
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/50750701
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