Android PopupWindow中ArrayList的SetText NullPointerException。安卓
我想在文本视图中为弹出窗口显示一个数组。仅随机从数组中选择1项。在这种情况下,我在我的Android PopupWindow中ArrayList的SetText NullPointerException。安卓,android,arraylist,android-popupwindow,Android,Arraylist,Android Popupwindow,我想在文本视图中为弹出窗口显示一个数组。仅随机从数组中选择1项。在这种情况下,我在我的main活动中使用一个ArrayList并调用randomArray()来显示。 它在屏幕_popup.xml上不起作用。但它在Main_activity.xml中确实起作用。我正在使用TextView textView1作为主要活动&TextView txtViewArrayContent作为弹出窗口。我认为TextView已正确初始化,但与setContentView有关?任何指点都很好,谢谢 日志cat中
main活动中使用一个ArrayList
并调用randomArray()
来显示。
它在屏幕_popup.xml上不起作用。但它在Main_activity.xml中确实起作用。我正在使用TextView textView1
作为主要活动&TextView txtViewArrayContent
作为弹出窗口。我认为TextView已正确初始化,但与setContentView
有关?任何指点都很好,谢谢
日志cat中的错误为:
07-17 09:25:34.655 25779-25779/com.example.testarray_02 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.testarray_02, PID: 25779
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.testarray_02/com.example.testarray_02.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
主要活动包括:
public class MainActivity extends Activity {
Button btnClosePopup;
Button btnCreatePopup;
TextView newArray;
String item;
//***** Random Generator & ArrayList *****
final Random randomGenerator = new Random();
final ArrayList sample = new ArrayList() {{ add("Random Facts about Stuff"); add("Random Facts about Stuff 2"); add("Random Facts about Stuff 3"); add("Random Facts about Stuff 4");}};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Works - main activity layout
// newArray = (TextView)findViewById(R.id.textView1);
// Does NOT work. ... popup layout
newArray = (TextView)findViewById(R.id.txtViewArrayContent);
randomArray();
btnCreatePopup = (Button) findViewById(R.id.button1);
btnCreatePopup.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
customPopupWindow(v);
}
});
}
private void randomArray() {
//setContentView(R.layout.screen_popup);
item = (String) sample.get(randomGenerator.nextInt(sample.size()));
newArray.setText(item); // Error logcat points to this line
// Null Exception Error
}
private PopupWindow popupWin;
private void customPopupWindow(View v){
try {
LayoutInflater inflater = (LayoutInflater) MainActivity.this
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View layout = inflater.inflate(R.layout.screen_popup,
(ViewGroup) findViewById(R.id.popup_element));
popupWin = new PopupWindow(layout, 600, 600, true);
popupWin.showAtLocation(layout, Gravity.CENTER, 0, 0);
btnClosePopup = (Button) layout.findViewById(R.id.btn_close_popup);
btnClosePopup.setOnClickListener(cancel_button_click_listener);
} catch (Exception e) {
e.printStackTrace();
}
}
private View.OnClickListener cancel_button_click_listener = new View.OnClickListener() {
public void onClick(View v) {
popupWin.dismiss();
}
};
}
XML屏幕弹出窗口的片段
<TextView
android:id="@+id/txtViewArrayContent"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="5sp"
android:text="" />
您试图通过在
activity\u main.xml
文件中按id查找来初始化newArray
,但它不在那里,因此您会得到NullPointerException
。要修复代码,请从onCreate()
方法中删除newArray
初始化和调用randomArray()
,并将其添加到customPopupWindwo(视图v)
中,如下所示:
private void customPopupWindow(View v) {
LayoutInflater inflater = (LayoutInflater) MainActivity.this
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View layout = inflater.inflate(R.layout.screen_popup,
(ViewGroup) findViewById(R.id.popup_element));
newArray = (TextView) layout.findViewById(R.id.txtViewArrayContent);
//omitted rest for brevity
}
它不存在/在单击按钮之前未充气