我有一个可扩展列表的代码,我想在列表视图的子组中有一个复选框,并检查是否有一个复选框被选中。 问题是,当我检查复选框是否被选中时,我得到一个NULL指针异常。检查复选框是否被选中返回空指针
你能告诉我什么是错的吗?
这里是我的代码 - 我已经编辑了代码来扩充child_row.xml的视图,该视图拥有该复选框,但仍然得到空指针,我做错了什么?!?!
package send.Shift;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import android.app.ExpandableListActivity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.Window;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.ExpandableListView;
import android.widget.SimpleExpandableListAdapter;
import android.widget.TextView;
public class Shifts extends ExpandableListActivity implements
OnCheckedChangeListener {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.list);
SimpleExpandableListAdapter expListAdapter = new SimpleExpandableListAdapter(
this, createGroupList(), R.layout.group_row,
new String[] { "Group Item" }, new int[] { R.id.row_name },
createChildList(), R.layout.child_row,
new String[] { "Sub Item" }, new int[] { R.id.grp_child });
getExpandableListView().setGroupIndicator(
getResources().getDrawable(R.drawable.expander_group));
ExpandableListView EX = (ExpandableListView) findViewById(android.R.id.list);
EX.setAdapter(expListAdapter);
final CheckBox childBox = (CheckBox) findViewById(R.id.childBOX);
final TextView choosenGroup = (TextView) findViewById(R.id.choosen);
LayoutInflater inflater = LayoutInflater.from(Shifts.this);
View view2 = inflater.inflate(R.layout.child_row, null);
childBox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView,
boolean isChecked) {
// TODO Auto-generated method stub
if(childBox.isChecked() == true){
choosenGroup.setText("Shift Set");
}
}
});
}
下面是一些logcat的日志:
12-23 07:38:00.644: W/dalvikvm(880): threadid=1: thread exiting with uncaught exception (group=0x40015560)
12-23 07:38:00.654: E/AndroidRuntime(880): FATAL EXCEPTION: main
12-23 07:38:00.654: E/AndroidRuntime(880): java.lang.RuntimeException: Unable to start activity ComponentInfo{send.Shift/send.Shift.Shifts}: java.lang.NullPointerException
12-23 07:38:00.654: E/AndroidRuntime(880): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
12-23 07:38:00.654: E/AndroidRuntime(880): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
12-23 07:38:00.654: E/AndroidRuntime(880): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
12-23 07:38:00.654: E/AndroidRuntime(880): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
12-23 07:38:00.654: E/AndroidRuntime(880): at android.os.Handler.dispatchMessage(Handler.java:99)
12-23 07:38:00.654: E/AndroidRuntime(880): at android.os.Looper.loop(Looper.java:123)
12-23 07:38:00.654: E/AndroidRuntime(880): at android.app.ActivityThread.main(ActivityThread.java:3683)
12-23 07:38:00.654: E/AndroidRuntime(880): at java.lang.reflect.Method.invokeNative(Native Method)
12-23 07:38:00.654: E/AndroidRuntime(880): at java.lang.reflect.Method.invoke(Method.java:507)
12-23 07:38:00.654: E/AndroidRuntime(880): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-23 07:38:00.654: E/AndroidRuntime(880): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-23 07:38:00.654: E/AndroidRuntime(880): at dalvik.system.NativeStart.main(Native Method)
12-23 07:38:00.654: E/AndroidRuntime(880): Caused by: java.lang.NullPointerException
12-23 07:38:00.654: E/AndroidRuntime(880): at send.Shift.Shifts.onCreate(Shifts.java:41)
12-23 07:38:00.654: E/AndroidRuntime(880): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
12-23 07:38:00.654: E/AndroidRuntime(880): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
12-23 07:38:00.654: E/AndroidRuntime(880): ... 11 more
谢谢,我已经添加了logcat。我知道哪一行是空的,但我不知道为什么。我在某处读过它可能与这个CheckBox不在布局上我在setContent上膨胀的事实有关? – Yosi199 2011-12-23 07:52:47
正如我在这里所说的:“它可能是你的id是childBox而不是childBOX,或者它不在R.layout.list中”。 'findViewById'函数实际上只会返回屏幕上的东西,在这种情况下,它应该在'R.layout.list'中。如果不是,那么我引用的行将返回'null',并且您正在有效地调用'null.isChecked()',这会显然给你一个空指针。 – Nanne 2011-12-23 07:55:37
OKKKK所以现在我明白了。我的列表XML是保存ExpandableListView的东西,但它本身不包含复选框 - 复选框位于为列表视图的子项设置的不同布局xml中。我如何从不同的XML引用该复选框? – Yosi199 2011-12-23 08:00:08