Question

我正在尝试使用customAdapter类添加功能更新listView。但是我遇到了奇怪的行为。添加元素的第一次尝试有效，但在此之后，listView不会更新。我看过许多论坛（这就是我到目前为止的方式），但这是我无法取得进展的地方。

这是代码： HomeScreen.java

package com.apress.gerber.mathematicalcalculator;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.content.Intent;


public class HomeScreen extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home_screen);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_home_screen, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void onClickLogTable(View view){
        Intent logTableLauncherInternt = new Intent(this, LogTable.class);
        startActivity(logTableLauncherInternt);
    }
}

LogTable.java

package com.apress.gerber.mathematicalcalculator;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.EditText;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;

import java.util.List;


public class LogTable extends AppCompatActivity {

    public customAdapter c;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_log_table);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }

    public void onClickCalculate(View view){
        EditText logBaseValue = (EditText) findViewById(R.id.logBaseValue);

        if(logBaseValue.getText().toString().length()<=0) {
            Toast.makeText(LogTable.this, "Input Something", Toast.LENGTH_LONG).show();
            return;
        }

        int logBase = Integer.parseInt(logBaseValue.getText().toString());
        logBaseValue.setText(String.format("%d",logBase));

        if(logBase != logBase)
            Toast.makeText(LogTable.this, "Invalid Input", Toast.LENGTH_LONG).show();



        String[] numbers = {"1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16"};
        c = new customAdapter(this, numbers, logBase);
        ListAdapter logTableAdapter = c;

        ListView logTable = (ListView) findViewById(R.id.logTable);
        logTable.setAdapter(logTableAdapter);


        logTable.setOnScrollListener(new AbsListView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                if(firstVisibleItem+visibleItemCount>=(totalItemCount-3)){
                    Integer asd = (int) Math.ceil(Math.random()*100);
                    Log.d("RedMango", "" + asd);
                    c.add(Integer.toString(asd));
                }
            }
        });

    }

}

customAdapter.java

package com.apress.gerber.mathematicalcalculator;

import android.content.Context;
import android.content.Intent;
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 java.util.List;

/**
 * Created by as on 10/10/15.
 */
class customAdapter extends ArrayAdapter<String>{

    private static List<String> ListValues = new ArrayList<String>();
    private static List<String> LogValues = new ArrayList<String>();
    private Integer BaseValue;

    public customAdapter(Context context, String[] listValues, int baseValue) {
        super(context, R.layout.infiniteloglayout, listValues);
        for(int i=0; i<listValues.length-1; i++){
            ListValues.add(listValues[i]);
            LogValues.add(Double.toString(Math.log(Double.parseDouble(listValues[i])) / Math.log(baseValue)));
        }
        BaseValue = baseValue;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater logInflater = LayoutInflater.from(getContext());
        View infiniteloglayout = logInflater.inflate(R.layout.infiniteloglayout, parent, false);

        TextView value = (TextView) infiniteloglayout.findViewById(R.id.value);
        TextView logValue = (TextView) infiniteloglayout.findViewById(R.id.logValue);

        value.setText(ListValues.get(position));
        logValue.setText(LogValues.get(position));
        return infiniteloglayout;

    }

    public void add(String value) {
        ListValues.add(value);
        LogValues.add(Double.toString(Math.log(Double.parseDouble(value)) / Math.log(BaseValue)));
        Log.d("RedMango", "ListValues " + ListValues.size());
        this.notifyDataSetChanged();
    }
}

问题是在调用onScrollListner之后，第一个随机元素被添加到屏幕上的列表中。但是之后，屏幕上的列表没有添加内容。我尝试记录数据，我可以确认函数正在运行，数据正在添加到适配器的列表中，但是数据没有被更新（第一个条目除外）。任何人都可以指出我犯了错误的地方。我也尝试将notifyDataSetChanged移出类，但这并未改变行为。

注意：这是我在stackoverflow上的第一篇文章，所以如果我犯了任何错误（比如违反了一些潜规则），请告诉我。

Answer 1

您已经声明了两个不同的集合，一个数组和另一个列表，并使用其中一个，即数组作为适配器的实际数据，另一个仅在getView中用于getItem。有两种方法可以解决这个问题：

在customAdapter上的add方法中。而不是
```
public void add(String value) {
      ListValues.add(value);
```
你应该使用
```
    public void add(String value) {
          super.add(value);
```
从自定义适配器中删除ListValues变量，并在getView中使用
```
    value.setText(getItem(position));
```
代替。你正在使用for(int i=0; i<listValues.length-1; i++){ 您应该将其更改为for(int i=0; i<listValues.length; i++){

或者您应该将数据作为arraylist从活动中传递出去。例：在您的活动中将适配器更改为：

String[] numbers = {"1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16"};
ArrayList<String> arrayListValues = new ArrayList<>(Arrays.asList(numbers));
c = new customAdapter(this, arrayListValues, logBase);

现在将适配器更改为：

private static ArrayList<String> ListValues;
private static List<String> LogValues = new ArrayList<String>();
private Integer BaseValue;

public customAdapter(Context context, ArrayList<String> listValues, int baseValue) {
super(context, R.layout.infiniteloglayout, listValues);
this.ListValues = listValues;
for (int i = 0; i < listValues.size(); i++) {
    LogValues.add(Double.toString(Math.log(Double.parseDouble(listValues[i])) / Math.log(baseValue)));
}
BaseValue = baseValue;
}

notifyDataSetChanged没有更新listView

1 个答案: