我有一个全局变量，我在我的应用程序上下文中初始化，以使所有类都可以访问它。
在一个屏幕上，我有一个带适配器的列表，我想要访问名为＆＃34; horizontalBoxPosition＆＃34;，
的变量这是我获取数据的方式
String horitonalBoxPosition, verticalBoxPosition;
horitonalBoxPosition = ((appContext) getContext()).getHorizontalBoxPosition();
但它输出错误：
Attempt to invoke virtual method 'java.lang.String apps.radwin.wintouch.appContext.getHorizontalBoxPosition()' on a null object reference
如何解决这个问题？尝试了许多建议，但他们没有成功。
这是我的完整适配器：
package apps.radwin.wintouch.adapters;
import android.content.Context;
import android.graphics.Color;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;
import java.util.ArrayList;
import apps.radwin.wintouch.Aligment_Scan_Activity;
import apps.radwin.wintouch.R;
import apps.radwin.wintouch.appContext;
import apps.radwin.wintouch.models.AligmentListModel;
/**
* Created by shay_v on 04/05/2016.
*/
public class AligmentScanListAdapter extends ArrayAdapter<AligmentListModel> {
public AligmentScanListAdapter(Context context, ArrayList<AligmentListModel> aligmentModel) {
super(context, 0, aligmentModel);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// Get the data item for this position
AligmentListModel aligmentModelData = getItem(position);
// Check if an existing view is being reused, otherwise inflate the view
if (convertView == null) {
convertView = LayoutInflater.from(getContext()).inflate(R.layout.list_layout_aligment_scan, parent, false);
}
// Lookup view for data population
// TextView spliceNumberTextVew = (TextView) convertView.findViewById(R.id.list_layout_splice_textView); //casting
//
// TextView scannedUpTextView = (TextView) convertView.findViewById(R.id.list_layout_scanned_up_textView); //casting
// TextView scannedNormalTextView = (TextView) convertView.findViewById(R.id.list_layout_scanned_normal_textView); //casting
// TextView scannedButtomTextView = (TextView) convertView.findViewById(R.id.list_layout_scanned_buttom_textView); //casting
//
// TextView baseStationUpTextView = (TextView) convertView.findViewById(R.id.list_layout_base_up_textView); //casting
// TextView baseStationNormalTextView = (TextView) convertView.findViewById(R.id.list_layout_base_normal_textView); //casting
// TextView baseStationButtomTextView = (TextView) convertView.findViewById(R.id.list_layout_base_buttom_textView); //casting
//Log.d ("myLogs", "drawing list");
//lookup the views to change color later
View leftSquare = (View) convertView.findViewById(R.id.aligmentList_LeftSquare);
View middleSquare = (View) convertView.findViewById(R.id.aligmentList_middleSquare);
View rightSquare = (View) convertView.findViewById(R.id.aligmentList_RightSquare);
View leftSquareFrame = (View) convertView.findViewById(R.id.aligmentList_LeftSquare_frame);
View middleSquareFrame = (View) convertView.findViewById(R.id.aligmentList_middleSquare_frame);
View rightSquareFrame = (View) convertView.findViewById(R.id.aligmentList_RightSquare_frame);
// Populate the data into the template view using the data object
// spliceNumberTextVew.setText(aligmentModelData.cellNumber);
//
// scannedUpTextView.setText(aligmentModelData.sectorsScannedHigh);
// scannedNormalTextView.setText(aligmentModelData.sectorsScannedMedium);
// scannedButtomTextView.setText(aligmentModelData.sectorsScannedLow);
//
// baseStationUpTextView.setText(aligmentModelData.basePointsRecivedHigh);
// baseStationNormalTextView.setText(aligmentModelData.basePointsRecivedMedium);
// baseStationButtomTextView.setText(aligmentModelData.basePointsRecivedLow);
if (aligmentModelData.sectorsScannedHigh.matches("true")) { //colors the left colum, the hight one
leftSquare.setBackgroundColor(Color.argb(255, 0, 204, 102));
} else {
leftSquare.setBackgroundColor(Color.argb(255, 244, 224, 224));
}
if (aligmentModelData.sectorsScannedMedium.matches("true")) { //colors the middle colum, the hight one
middleSquare.setBackgroundColor(Color.argb(255, 0, 204, 102));
} else {
middleSquare.setBackgroundColor(Color.argb(255, 244, 224, 224));
}
if (aligmentModelData.sectorsScannedLow.matches("true")) { //colors the low colum, the hight one
rightSquare.setBackgroundColor(Color.argb(255, 0, 204, 102));
} else {
rightSquare.setBackgroundColor(Color.argb(255, 244, 224, 224));
}
/////////////
//color the base stations
int basePointsHighLength = aligmentModelData.basePointsRecivedHigh.toString().length(); // colors the rest of your basepoints found
int basePointsRecivedMedium = aligmentModelData.basePointsRecivedMedium.toString().length();
int basePointsRecivedLow = aligmentModelData.basePointsRecivedLow.toString().length();
if (basePointsHighLength > 2) { //colors the left colum, the hight one
leftSquare.setBackgroundColor(Color.argb(255, 255, 51, 0));
}
if (basePointsRecivedMedium > 2) { //colors the middle colum, the hight one
middleSquare.setBackgroundColor(Color.argb(255, 255, 51, 0));
}
if (basePointsRecivedLow > 2) { //colors the low colum, the hight one
rightSquare.setBackgroundColor(Color.argb(255, 255, 51, 0));
}
//removing the background frame
String horitonalBoxPosition, verticalBoxPosition;
horitonalBoxPosition = ((appContext) getContext()).getHorizontalBoxPosition();
Log.d ("myLogs", "horizontal Position"+horitonalBoxPosition);
return convertView;
}
}
我的完整上下文类：
package apps.radwin.wintouch;
import android.app.Application;
import android.util.Log;
import apps.radwin.wintouch.screenManagers.AligmentManager;
/**
* Created by shay_v on 16/05/2016.
*/
//////////////////////////////////////////////////////////////////////////////
//THIS IS THE APP CONTEXT OF THE APPLICATION - COUTION REQUIRED - HDNLE GENTLY
//////////////////////////////////////////////////////////////////////////////
public class appContext extends Application {
private AligmentManager aligmentManagerVar = new AligmentManager(); // making aligment Manager accecible to all classes
private String horizontalBoxPosition = "0";
private String verticalBoxPosition = "0";
public String getVerticalBoxPosition() {
Log.d ("myLogs", "getsVertical: "+verticalBoxPosition);
return verticalBoxPosition;
}
public void setVerticalBoxPosition(String verticalBoxPosition) {
Log.d ("myLogs", "setsVertical: "+verticalBoxPosition);
this.verticalBoxPosition = verticalBoxPosition;
}
public String getHorizontalBoxPosition() {
return horizontalBoxPosition;
}
public void setHorizontalBoxPosition(String horizontalBoxPosition) {
this.horizontalBoxPosition = horizontalBoxPosition;
}
public AligmentManager getAligmentManagerVar() {
return aligmentManagerVar;
}
}
完整错误日志：
06-02 11:12:08.091 4480-4480/apps.radwin.wintouch D/AndroidRuntime: Shutting down VM
06-02 11:12:08.101 4480-4480/apps.radwin.wintouch E/AndroidRuntime: FATAL EXCEPTION: main
Process: apps.radwin.wintouch, PID: 4480
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String apps.radwin.wintouch.appContext.getHorizontalBoxPosition()' on a null object reference
at apps.radwin.wintouch.adapters.AligmentScanListAdapter.getView(AligmentScanListAdapter.java:114)
at android.widget.AbsListView.obtainView(AbsListView.java:2929)
at android.widget.ListView.measureHeightOfChildren(ListView.java:1305)
at android.widget.ListView.onMeasure(ListView.java:1212)
at android.view.View.measure(View.java:20151)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:716)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:462)
at android.view.View.measure(View.java:20151)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6328)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:664)
at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:90)
at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1149)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:729)
at android.view.View.measure(View.java:20151)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:1075)
at android.view.View.measure(View.java:20151)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6328)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:20151)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6328)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:747)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:629)
at android.view.View.measure(View.java:20151)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6328)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.view.View.measure(View.java:20151)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6328)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:747)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:629)
at android.view.View.measure(View.java:20151)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6328)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.view.View.measure(View.java:20151)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6328)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:3158)
at android.view.View.measure(View.java:20151)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2594)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1549)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1841)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1437)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7397)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:920)
at android.view.Choreographer.doCallbacks(Choreographer.java:695)
at android.view.Choreographer.doFrame(Choreographer.java:631)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:906)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7224)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120
答案 0 :(得分：0)
as + mgcaguioa用于回复将所有内容更改为静态 像魅力一样工作！ 日Thnx
对于未来的用户来说，这是一个新的appcontext，向您展示我的所作所为：
package apps.radwin.wintouch;
import android.app.Application;
import apps.radwin.wintouch.screenManagers.AligmentManager;
/**
* Created by shay_v on 16/05/2016.
*/
//////////////////////////////////////////////////////////////////////////////
//THIS IS THE APP CONTEXT OF THE APPLICATION - COUTION REQUIRED - HDNLE GENTLY
//////////////////////////////////////////////////////////////////////////////
public class appContext extends Application {
private AligmentManager aligmentManagerVar = new AligmentManager(); // making aligment Manager accecible to all classes
private static String horizontalBoxPosition;
private static String verticalBoxPosition;
public static String getVerticalBoxPosition() {
return verticalBoxPosition;
}
public static void setVerticalBoxPosition(String verticalBoxPosition) {
verticalBoxPosition = verticalBoxPosition;
}
public static String getHorizontalBoxPosition() {
return horizontalBoxPosition;
}
public static void setHorizontalBoxPosition(String horizontalBoxPosition) {
horizontalBoxPosition = horizontalBoxPosition;
}
public AligmentManager getAligmentManagerVar() {
return aligmentManagerVar;
}
}
答案 1 :(得分：-1)
尝试将此构造函数用于'AligmentScanListAdapter'类：
public Context con;
public AligmentScanListAdapter(Context context, ArrayList<AligmentListModel> aligmentModel) {
super(context, 0, aligmentModel);
this.con=context;
}
之后使用代码而不是removing the background frame代码：
//removing the background frame
String horitonalBoxPosition, verticalBoxPosition;
horitonalBoxPosition = this.con.getHorizontalBoxPosition();
Log.d ("myLogs", "horizontal Position"+horitonalBoxPosition);
return convertView;