Android 更改listview项的textcolor时出现NullPointerException
重写getView方法以更改列表项的textcolor-Android 更改listview项的textcolor时出现NullPointerException,android,listview,nullpointerexception,Android,Listview,Nullpointerexception,重写getView方法以更改列表项的textcolor- aa = new ArrayAdapter(this,android.R.layout.simple_list_item_1, al) { @Override public View getView(int position, View convertView, ViewGroup parent) { View view = super.getView(position, conv
aa = new ArrayAdapter(this,android.R.layout.simple_list_item_1, al) {
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view = super.getView(position, convertView, parent);
TextView tv = (TextView)convertView.findViewById(android.R.id.text1);
tv.setTextColor(Color.WHITE);
tv.setVisibility(View.VISIBLE);
return view;
}
} ;
日志:
-Process: com.example.sairav.app3, PID: 1470
***java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
at com.example.sairav.app3.MainActivity$1.getView(MainActivity.java:38)***
at android.widget.AbsListView.obtainView(AbsListView.java:2344)
at android.widget.ListView.makeAndAddView(ListView.java:1864)
at android.widget.ListView.fillDown(ListView.java:698)
at android.widget.ListView.fillFromTop(ListView.java:759)
at android.widget.ListView.layoutChildren(ListView.java:1673)
at android.widget.AbsListView.onLayout(AbsListView.java:2148)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.AbsoluteLayout.onLayout(AbsoluteLayout.java:123)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
第一次调用getView时,convertView为null。调用super并将其返回值赋给view,会使convertView未初始化,从而导致崩溃
convertView = super.getView(position, convertView, parent);
TextView tv = (TextView)convertView.findViewById(android.R.id.text1);
tv.setTextColor(Color.WHITE);
tv.setVisibility(View.VISIBLE);
return convertView;
编辑:
android.R.layout.simple\u list\u item\u 1
只包含一个TextView
,因此要使用findViewById,您可以强制转换super.getView
的返回值
convertView = super.getView(position, convertView, parent);
((TextView)convertView).setTextColor(Color.WHITE);
((TextView)convertView).setVisibility(View.VISIBLE);
return convertView;
//使用视图而不是convertview
TextView tv = (TextView)view.findViewById(android.R.id.text1);
tv.setTextColor(Color.WHITE);
tv.setVisibility(View.VISIBLE);
return view;
}
} ;
TextView tv = (TextView)view.findViewById(android.R.id.text1);
tv.setTextColor(Color.WHITE);
tv.setVisibility(View.VISIBLE);
return view;
}
} ;