Error: Android Swipe-up Card call button is giving the problem
Error: Android Swipe-up Card call button is giving the problem
我正在尝试制作向上滑动的卡片，但出现以下错误。请帮忙。我对 Android 编程还很陌生。
尝试后，我得出的结论是，如果我注释掉 java 文件中的所有代码，那么卡片就可以正常工作，但即查看卡片的按钮就是问题所在。 ..我猜。
MainActivity
public class MainActivity extends AppCompatActivity implements adapterCard.ListItemClickListener {
private BottomSheetBehavior historyCardBehavior;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LinearLayout linearCardLayout = findViewById(R.id.history_sheet);
historyCardBehavior = BottomSheetBehavior.from(linearCardLayout);
Button historyButton = findViewById(R.id.history_button);
historyButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
historyCardBehavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
}
});
}
}
mainActivity.xml
<androidx.coordinatorlayout.widget.CoordinatorLayout 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=".MainActivity">
<Button
android:id="@+id/history_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|bottom"
android:layout_marginStart="20dp"
android:layout_marginTop="100dp"
android:text="@string/history" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/white"
android:orientation="horizontal">
<ScrollView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@color/white">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="20dp">
</LinearLayout>
</ScrollView>
</LinearLayout>
<include
android:id="@+id/orderHistory_card"
layout="@layout/history_sheet" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
history_sheet.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/history_sheet"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/transparent"
android:orientation="vertical"
app:behavior_hideable="true"
app:behavior_peekHeight="80dp"
app:layout_behavior="@string/bottom_sheet_behavior">
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:cardBackgroundColor="@android:color/white"
app:cardCornerRadius="20dp"
app:cardElevation="20dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="15dp">
<View
android:layout_width="50dp"
android:layout_height="8dp"
android:layout_gravity="center"
android:layout_marginBottom="10dp"
android:background="#70000000"
android:outlineProvider="background"/>
</LinearLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
错误
2021-01-30 00:10:35.274 8461-8461/com.iwantjob.oneresto E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.iwantjob.oneresto, PID: 8461
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.iwantjob.oneresto/com.iwantjob.oneresto.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at com.google.android.material.bottomsheet.BottomSheetBehavior.from(BottomSheetBehavior.java:1632)
at com.iwantjob.oneresto.MainActivity.onCreate(MainActivity.java:35)
at android.app.Activity.performCreate(Activity.java:7136)
at android.app.Activity.performCreate(Activity.java:7127)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
2021-01-30 00:10:35.299 8461-8461/com.iwantjob.oneresto I/Process: Sending signal. PID: 8461 SIG: 9
如果有人能提供帮助，那将非常有帮助。
提前致谢。
app:layout_behavior="@string/bottom_sheet_behavior" 行在这里最吸引我的眼球。
@string/bottom_sheet_behavior 在您的项目中定义的是什么？应将布局行为属性分配给 "com.google.android.material.bottomsheet.BottomSheetBehavior"。
此外，从调用堆栈看来，您的 findViewById returns 为空。尝试使用 R.id.orderHistory_card 而不是 R.id.history_sheet 进行 linearCardLayout 查找。从长远来看，我建议研究 ViewBinding 以尽量减少围绕视图的样板代码并避免此类问题。
我正在尝试制作向上滑动的卡片，但出现以下错误。请帮忙。我对 Android 编程还很陌生。
尝试后，我得出的结论是，如果我注释掉 java 文件中的所有代码，那么卡片就可以正常工作，但即查看卡片的按钮就是问题所在。 ..我猜。
MainActivity
public class MainActivity extends AppCompatActivity implements adapterCard.ListItemClickListener {
private BottomSheetBehavior historyCardBehavior;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LinearLayout linearCardLayout = findViewById(R.id.history_sheet);
historyCardBehavior = BottomSheetBehavior.from(linearCardLayout);
Button historyButton = findViewById(R.id.history_button);
historyButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
historyCardBehavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
}
});
}
}
mainActivity.xml
<androidx.coordinatorlayout.widget.CoordinatorLayout 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=".MainActivity">
<Button
android:id="@+id/history_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|bottom"
android:layout_marginStart="20dp"
android:layout_marginTop="100dp"
android:text="@string/history" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/white"
android:orientation="horizontal">
<ScrollView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@color/white">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="20dp">
</LinearLayout>
</ScrollView>
</LinearLayout>
<include
android:id="@+id/orderHistory_card"
layout="@layout/history_sheet" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
history_sheet.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/history_sheet"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/transparent"
android:orientation="vertical"
app:behavior_hideable="true"
app:behavior_peekHeight="80dp"
app:layout_behavior="@string/bottom_sheet_behavior">
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:cardBackgroundColor="@android:color/white"
app:cardCornerRadius="20dp"
app:cardElevation="20dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="15dp">
<View
android:layout_width="50dp"
android:layout_height="8dp"
android:layout_gravity="center"
android:layout_marginBottom="10dp"
android:background="#70000000"
android:outlineProvider="background"/>
</LinearLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
错误
2021-01-30 00:10:35.274 8461-8461/com.iwantjob.oneresto E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.iwantjob.oneresto, PID: 8461
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.iwantjob.oneresto/com.iwantjob.oneresto.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at com.google.android.material.bottomsheet.BottomSheetBehavior.from(BottomSheetBehavior.java:1632)
at com.iwantjob.oneresto.MainActivity.onCreate(MainActivity.java:35)
at android.app.Activity.performCreate(Activity.java:7136)
at android.app.Activity.performCreate(Activity.java:7127)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
2021-01-30 00:10:35.299 8461-8461/com.iwantjob.oneresto I/Process: Sending signal. PID: 8461 SIG: 9
如果有人能提供帮助，那将非常有帮助。 提前致谢。
app:layout_behavior="@string/bottom_sheet_behavior" 行在这里最吸引我的眼球。
@string/bottom_sheet_behavior 在您的项目中定义的是什么？应将布局行为属性分配给 "com.google.android.material.bottomsheet.BottomSheetBehavior"。
此外，从调用堆栈看来，您的 findViewById returns 为空。尝试使用 R.id.orderHistory_card 而不是 R.id.history_sheet 进行 linearCardLayout 查找。从长远来看，我建议研究 ViewBinding 以尽量减少围绕视图的样板代码并避免此类问题。