自定义ListView没有显示任何数据

Question

我对自定义列表视图有一些问题，自定义列表视图没有显示我给他们的任何数据。我尝试放置adapter.notifyDataSetChanged((；但两者似乎没有什么区别。从数据库中获取的数据没有显示

这是我的活动

import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
public class Transaksi extends AppCompatActivity {
ListView LISTVIEW;
ArrayList<Transaction> translist;
Transaction transaction;
DatabaseHelper handler;
CursorAdaptor1 adapter;
public static int okko;
FloatingActionButton fab;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.trankk);
setRequestedOrientation (ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
handler = new DatabaseHelper(this);
Cursor cursor = handler.viewTrans(getIntent().getIntExtra("EXTRA_ID",0));
fab = (FloatingActionButton) findViewById(R.id.fab);
okko = getIntent().getIntExtra("EXTRA_ID",0);
translist = new ArrayList<>();
adapter = new CursorAdaptor1(Transaksi.this, R.layout.adapter_view_layout,translist);
LISTVIEW = (ListView) findViewById(R.id.LISTVIEW);
LISTVIEW.setAdapter(adapter);
int a = cursor.getCount();
cursor.moveToFirst();
Toast.makeText(this, ""+cursor.getString(1)+"  "+cursor.getString(2)+"  "+cursor.getString(3)+"  "+cursor.getDouble(4)+"  "+cursor.getDouble(5)+"  "+cursor.getDouble(6), Toast.LENGTH_SHORT).show();

if(cursor.moveToFirst() && a >= 1){
while (cursor.moveToNext()){
transaction = new Transaction(cursor.getString(1),cursor.getString(2),cursor.getString(3),cursor.getDouble(4),cursor.getDouble(5),cursor.getDouble(6));
adapter.notifyDataSetChanged();
translist.add(transaction);
}
adapter.notifyDataSetChanged();
}else{
Toast.makeText(this, "There is not transaction yet!!", Toast.LENGTH_SHORT).show();
}
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
openDialog();
}
});

}
public void openDialog(){
ExampleDialog exampleDialog = new ExampleDialog();
exampleDialog.show(getSupportFragmentManager(),"Example Dialog");
}

这是我的适配器类

import android.content.Context;
import android.database.Cursor;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CursorAdapter;
import android.widget.TextView;
import com.example.werren.testapp.R;
import java.util.ArrayList;
public class CursorAdaptor1 extends ArrayAdapter<Transaction> {
private LayoutInflater mInflater;
private ArrayList<Transaction> transaction;
private int mViewResourceId;
public CursorAdaptor1(Context context, int textViewResourceId, ArrayList<Transaction> transactions){
super(context,textViewResourceId,transactions);
this.transaction = transactions;
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
mViewResourceId = textViewResourceId;
}
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent){
return newView(position,convertView,parent);
}
public View newView(int position, View convertView, ViewGroup parent) {
if(convertView == null){
convertView = mInflater.inflate(mViewResourceId,null);
}
Transaction trans = transaction.get(position);
if(trans != null){
TextView tanggal = (TextView) convertView.findViewById(R.id.FirstText);
TextView cur_beli = (TextView) convertView.findViewById(R.id.SecondText);
TextView cur_jual = (TextView) convertView.findViewById(R.id.ThirdText);
TextView jumlah = (TextView) convertView.findViewById(R.id.FourthText);
TextView kurs = (TextView) convertView.findViewById(R.id.FifthText);
TextView total = (TextView) convertView.findViewById(R.id.SixthText);
String a = String.valueOf(trans.getJumlah1());
String b = String.valueOf(trans.getKurs1());
String c = String.valueOf(trans.getTotal1());
tanggal.setText(trans.getTanggal1());
cur_beli.setText(trans.getCur_beli1());
cur_jual.setText(trans.getCur_jual1());
jumlah.setText(a);
kurs.setText(b);
total.setText(c);
}
return convertView;
}

}

这是while loop crash 的Logcat

2020-03-29 03:33:50.235 11124-11124/com.example.werren.testapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.werren.testapp, PID: 11124
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.werren.testapp/com.example.werren.testapp.Transaksi}: android.database.CursorIndexOutOfBoundsException: Index 1 requested, with a size of 1
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: android.database.CursorIndexOutOfBoundsException: Index 1 requested, with a size of 1
at android.database.AbstractCursor.checkPosition(AbstractCursor.java:468)
at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:50)
at com.example.werren.testapp.Transaksi.onCreate(Transaksi.java:67)
at android.app.Activity.performCreate(Activity.java:7009)
at android.app.Activity.performCreate(Activity.java:7000)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
at android.app.ActivityThread.-wrap11(Unknown Source:0) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
at android.os.Handler.dispatchMessage(Handler.java:106) 
at android.os.Looper.loop(Looper.java:164) 
at android.app.ActivityThread.main(ActivityThread.java:6494) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 

Answer 1

1. adapter.notifyDataSetChanged();应该在LISTVIEW.setAdapter(adapter);之后，而不是之前。建议将new CursorAdaptor1重新定位到translist = new ArrayList<>();之后。然后，您可以在while (cursor.moveToNext()){ ... }之后使用.notifyDataSetChange()

translist = new ArrayList<>();
//fixme-add-start
adapter = new CursorAdaptor1(Transaksi.this, R.layout.adapter_view_layout,translist);
//    adapter.notifyDataSetChanged();  //fixme:bug found
LISTVIEW = (ListView) findViewById(R.id.LISTVIEW);
LISTVIEW.setAdapter(adapter);
//fixme-add-end

if(cursor.moveToFirst() && a >= 1){
while (cursor.moveToNext()){
//...
}
//      adapter = new CursorAdaptor1(Transaksi.this, R.layout.adapter_view_layout,translist);  //fixme:del
adapter.notifyDataSetChanged();
//      LISTVIEW = (ListView) findViewById(R.id.LISTVIEW);  //fixme:del
//      LISTVIEW.setAdapter(adapter);  //fixme:del

2. 在CursorAdaptor1类中，不调用newView()。需要添加overridegetView()函数才能调用newView()。还添加了if (convertView == null) {检查

@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
return newView(position, convertView, parent);
}
public View newView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {  //fixme:add
convertView = mInflater.inflate(mViewResourceId, null);
}  //fixme:add
Transaction trans = transaction.get(position);
// ...