【发布时间】：2021-11-21 05:53:16
【问题描述】：
我目前正在做我的最后一个项目，但我卡住了。
我有 Firebase 实时数据库，它与我用 Android (Java) 编写的移动应用程序相连。 The database on which I am working has the following structure:
解决方案的想法是，我在 7 天（当前日期）中从数据库中获取 ukpromet 并将其保存到 ArrayList 中，该 ArrayList 在片段中生成bar chart。
现在的代码：
public class TjednoIzvjesceFragment extends Fragment {
final List<Float> tjednoIzvjesce = new ArrayList<>();
public ArrayList<BarEntry> entries = new ArrayList<>();
String korisnik, year, month, day;
Float ukpromet;
Integer dayx;
Integer monthx;
Integer yearx;
// Baza
FirebaseDatabase rootNode;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_tjedno_izvjesce, container, false);
BarChart barChart = view.findViewById(R.id.barChart);
// Testing ArrayList and Bar Chart
//entries.add(new BarEntry(0,2));
korisnik = ((HomeActivity) requireActivity()).korisnickoIme;
// Current date
String sadasnjiDatum = new SimpleDateFormat("dd/MM/yyyy", Locale.getDefault()).format(new Date());
//Current date in string
String[] separated = sadasnjiDatum.split("/");
dan = separated[0];
month = separated[1];
year = separated[2];
//Current date in integer
int danasdd = Integer.parseInt(dan);
int monthdd = Integer.parseInt(month);
int yeardd = Integer.parseInt(year);
String korisnik = ((HomeActivity) requireActivity()).korisnickoIme;
// Putanja do baze smjena vozaca
rootNode = FirebaseDatabase.getInstance();
DatabaseReference reference = rootNode.getReference("Vozaci");
// Current date for work in integer
dayx = todaydd;
monthx = monthdd;
yearx = yeardd;
// 7 days
int counter = 7;
for(int i = 0; i < counter; i++){
if (dayx <= 0) {
...
}
// DatabaseReference danPutanja = reference.child(korisnik).child("smjene").child(String.valueOf(yearx)).child("09").child(String.valueOf(dayx));
DatabaseReference danPutanja = reference.child(korisnik).child("smjene").child("2021").child("09").child("13");
readData(danPutanja,i, entries -> {
});
dayx--;
}
ArrayList<String> datumi = new ArrayList<>();
datumi.add("13.09");
datumi.add("14.09");
datumi.add("15.09");
datumi.add("16.09");
datumi.add("17/09");
datumi.add("18./09");
datumi.add("19./09");
// Chart Data
BarDataSet bardataset = new BarDataSet(entries, "DateSet1");
bardataset.setColors(ColorTemplate.COLORFUL_COLORS);
BarData data = new BarData(bardataset);
data.setBarWidth(0.9f);
// Chart layout
barChart.setDrawBarShadow(false);
barChart.setDrawValueAboveBar(true);
barChart.setPinchZoom(false);
barChart.setDrawGridBackground(true);
barChart.setData(data); // set the data and list of labels into chart
barChart.animateY(2000);
barChart.invalidate();
barChart.getDescription().setEnabled(false);
// Legend
Legend legend = barChart.getLegend();
legend.setEnabled(false);
// X axis
XAxis xAxis = barChart.getXAxis();
//xAxis.setCenterAxisLabels(true);
xAxis.setEnabled(true);
//xAxis.setDrawGridLines(false);
xAxis.setPosition(XAxis.XAxisPosition.BOTTOM);
xAxis.setValueFormatter(new com.github.mikephil.charting.formatter.IndexAxisValueFormatter(datumi));
return view;
}
private void readData(DatabaseReference danPutanja, float counter, FirebaseCallback firebaseCallback){
danPutanja.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
String getUkpromet;
if (dataSnapshot.exists()) {
getUkpromet = dataSnapshot.child("ukPromet").getValue(String.class);
} else {
getUkpromet = "0";
}
ukpromet = Float.parseFloat(getUkpromet);
System.out.println(ukpromet);
tjednoIzvjesce.add(ukpromet);
entries.add(new BarEntry(counter,ukpromet));
Log.e("!__@::>", counter + " " + ukpromet);
firebaseCallback.onCallBack(entries);
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
Log.d("Error: ", error.getMessage());
}
});
}
private interface FirebaseCallback{
void onCallBack(ArrayList<BarEntry> entries);
}
}
问题是数组中没有添加任何内容。
E/AndroidRuntime: FATAL EXCEPTION: main
Process: hr.vsite.map.taxivodstvo, PID: 1314
java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
at com.github.mikephil.charting.buffer.BarBuffer.addBar(BarBuffer.java:37)
at com.github.mikephil.charting.buffer.BarBuffer.feed(BarBuffer.java:80)
at com.github.mikephil.charting.renderer.BarChartRenderer.drawDataSet(BarChartRenderer.java:144)
at com.github.mikephil.charting.renderer.BarChartRenderer.drawData(BarChartRenderer.java:82)
at com.github.mikephil.charting.charts.BarLineChartBase.onDraw(BarLineChartBase.java:237)
at android.view.View.draw(View.java:21421)
at android.view.View.updateDisplayListIfDirty(View.java:20298)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.View.draw(View.java:21153)
at android.view.ViewGroup.drawChild(ViewGroup.java:4388)
at androidx.drawerlayout.widget.DrawerLayout.drawChild(DrawerLayout.java:1426)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4149)
at android.view.View.draw(View.java:21424)
at android.view.View.updateDisplayListIfDirty(View.java:20298)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4372)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4345)
at android.view.View.updateDisplayListIfDirty(View.java:20258)
at android.view.ThreadedRenderer.updateViewTreeDisplayList(ThreadedRenderer.java:575)
at android.view.ThreadedRenderer.updateRootDisplayList(ThreadedRenderer.java:581)
at android.view.ThreadedRenderer.draw(ThreadedRenderer.java:654)
at android.view.ViewRootImpl.draw(ViewRootImpl.java:3610)
at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:3418)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2755)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1721)
E/AndroidRuntime: at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7598)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:966)
at android.view.Choreographer.doCallbacks(Choreographer.java:790)
at android.view.Choreographer.doFrame(Choreographer.java:725)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:951)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
我怎么理解，问题出现是因为the asynchronous behavior of Firebase API。
我查看了 Alex Mamo 先生的教程和几篇关于该问题的文章。我不确定它可能是什么？？？？任何人都知道如何使它工作？
【问题讨论】：
-
你的 onDataChange() 甚至被触发了吗？数据库的位置，欧洲？
-
是的，它被触发了。我可以在日志中看到它：` E/!__@::>: 0.0 705.0 I/System.out: 705.0 E/!__@::>: 1.0 705.0 I/System.out: 705.0 E/!__@: :>: 2.0 705.0 I/System.out: 705.0 E/!__@::>: 3.0 705.0 I/System.out: 705.0 E/!__@::>: 4.0 705.0 I/System.out: 705.0 E/ !__@::>: 5.0 705.0 I/System.out: 705.0 E/!__@::>: 6.0 705.0 D/AndroidRuntime: 关闭 VM E/AndroidRuntime: 致命异常: 主进程: hr.vsite.map。 taxivodstvo，PID：1314 java.lang.ArrayIndexOutOfBoundsException：长度=0； index=0 ` 数据库位置：美国 (us-central1)。
-
您在哪一行代码中遇到了这个错误？
标签： java android firebase-realtime-database mpandroidchart