Android Studio 中的动态 ListView：选择随机元素并更新列表视图

Question

public class MyWorkout extends AppCompatActivity {
    Button addExercise
    // Record how many clicks
    int clickCounter=0;
    private ListView mListView;
    ArrayList<String> listItems = new ArrayList<String>()
    ArrayAdapter<String> adapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        SetContentView(R.layout.activity_my_workout);
        Toolbar MyWorkouttoolbar = (Toolbar) findViewById(R.id.MyWorkouttoolbar);
        setSupportActionBar(MyWorkouttoolbar);
        listItems.add("Power Clean");
        listItems.add("Dead Lift");
        listItems.add("Hang Clean");
        listItems.add("Military Press");
        listItems.add("Leg Press");
        listItems.add("Squat");
        listItems.add("Bench MAX");
        listItems.add("Squat MAX");
        listItems.add("Stair Stepper");
        listItems.add("Treadmill");
        listItems.add("Bike");
        listItems.add("Elliptical");
        listItems.add("Bicep Curls");
        listItems.add("Dumb Bell Squats");
        listItems.add("Goblet Squats");
        listItems.add("Bar Bell Curls");
        listItems.add("Bar Bell Bench Press");
        listItems.add("Dumb Bell Bench Press");
        listItems.add("Incline Bar Bell Bench Press");
        listItems.add("Incline Dumb Bell Bench Press");
        listItems.add("Decline Dumb Bell Bench Press");
        listItems.add("Decline Bar Bell Bench Press");
        listItems.add("Dumb Bell Lunges");
        listItems.add("Bar Bell Lunges");
        listItems.add("Dumb Bell Flys");
        listItems.add("Tricep Push Downs");

        if (mListView == null) {
            mListView = (ListView) findViewById(R.id.MyWorkoutlistView);
        }
        adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,listItems);
        setListAdapter(adapter);
        addExercise = (Button) findViewById(R.id.addExercise);
        addExercise.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Collections.shuffle(listItems);
                adapter.getItem(4);
                adapter.notifyDataSetChanged();
            }
        });
     }

     private void updateListView(){
         ListView listView = (ListView)findViewById(R.id.MyWorkoutlistView);
     }

     // method which will handle dynamic insertion
     public void addItems(View v) {
        listItems.add("Clicked : "+clickCounter++);
        adapter.notifyDataSetChanged();
     }

     protected ListView getListView(){
         if (mListView==null){
             mListView = (ListView) findViewById(R.id.MyWorkoutlistView);
         }
         return mListView;
     }

     protected void setListAdapter(ListAdapter adapter){
         getListView().setAdapter(adapter);
     }

     protected ListAdapter getListAdapter(){
         ListAdapter adapter = getListView().getAdapter();
         if (adapter instanceof HeaderViewListAdapter){
            return ((HeaderViewListAdapter)adapter).getWrappedAdapter();
        } else {
            return adapter;
        }
    }

我有一个包含练习的列表视图。我想随机选择数组中的一个元素并将该随机元素添加到另一个列表视图中。

还可以将原来的练习列表视图更改为仅显示随机元素吗？

我是 android studio 的新手，所以如果我不清楚，请告诉我，我会更好地解释。谢谢你

Answer 1

我有一个包含练习的列表视图。我想随机选择数组中的一个元素并将该随机元素添加到另一个列表视图中。

你可以：

1. 使用Random.nextInt() 获取数组中的随机位置
2. 检索该位置的元素，即arr[selectedPosition]
3. 将元素放入第二个ListView 的适配器中，例如ArrayAdapter.add()。

如果你不使用ArrayAdapter，你需要实现你的添加元素的接口，或者你可以用ListView.setAdapter()创建和设置一个全新的适配器。

还有可能改变原来的运动列表视图只显示随机元素吗？

当然可以，但还有一些工作要做。如果你使用ArrayAdapter，你可以只使用clear()适配器，然后add()只显示你想要显示的元素。为了不丢失日期，您可以将所有练习保存在适配器外部的数组/列表中。

如果你不使用ArrayAdapter，而想实现你的自定义逻辑，记得修改后在适配器上调用notifyDataSetChanged()，让ListView知道自己刷新。

Answer 2

检查我的答案here 我解释了如何将动态元素添加到列表视图中。

以防万一……

private EditText editTxt;
private Button btn;
private ListView list;
private ArrayAdapter<String> adapter;
private ArrayList<String> arrayList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    editTxt = (EditText) findViewById(R.id.editText);
    btn = (Button) findViewById(R.id.button);
    list = (ListView) findViewById(R.id.listView);
    arrayList = new ArrayList<String>();

    // Adapter: You need three parameters 'the context, id of the layout (it will be where the data is shown),
    // and the array that contains the data
    adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_spinner_item, arrayList);

    // Here, you set the data in your ListView
    list.setAdapter(adapter);

    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            // this line adds the data of your EditText and puts in your array
            arrayList.add(editTxt.getText().toString());
            // next thing you have to do is check if your adapter has changed
            adapter.notifyDataSetChanged();
        }
    });
}

Answer 3

以编程方式向自定义 ListView 添加/删除项目。此示例显示如何在运行时使用 Java 代码向自定义 ListView 添加/删除项目。 参考这个链接： http://android-er.blogspot.in/2015/01/add-remove-items-to-custom-listview.html

编辑 1： MainActivity.java

package com.example.androidimageviewlist;

import java.util.ArrayList;
import java.util.List;

import android.support.v7.app.ActionBarActivity;
import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemLongClickListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {

  public class Item {
  Drawable ItemDrawable;
  String ItemString;
  Item(Drawable drawable, String t){
  ItemDrawable = drawable;
   ItemString = t;
    }
 }

 static class ViewHolder {
  ImageView icon;
  TextView text; 
  }

  public class ItemsListAdapter extends BaseAdapter {

  private Context context;
  private List<Item> list;

  ItemsListAdapter(Context c, List<Item> l){
   context = c;
   list = l;
  }

  @Override
   public int getCount() {
   return list.size();
  }

   @Override
   public Object getItem(int position) {
   return list.get(position);
  }

   @Override
  public long getItemId(int position) {
   return position;
  }

  @Override
  public View getView(int position, View convertView, ViewGroup parent) {
   View rowView = convertView;

   // reuse views
  if (rowView == null) {
   LayoutInflater inflater = ((Activity) context).getLayoutInflater();
   rowView = inflater.inflate(R.layout.row, null);

   ViewHolder viewHolder = new ViewHolder();
   viewHolder.icon = (ImageView) rowView.findViewById(R.id.rowImageView);
   viewHolder.text = (TextView) rowView.findViewById(R.id.rowTextView);
   rowView.setTag(viewHolder); 
  }

  ViewHolder holder = (ViewHolder) rowView.getTag();
  holder.icon.setImageDrawable(list.get(position).ItemDrawable);
  holder.text.setText(list.get(position).ItemString);

  return rowView;
  }

  public List<Item> getList(){
   return list;
  }
 }

 List<Item> items1, items2;
 ListView listView1, listView2;
 ItemsListAdapter myItemsListAdapter1, myItemsListAdapter2;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  listView1 = (ListView)findViewById(R.id.listview1);
  listView2 = (ListView)findViewById(R.id.listview2);

  initItems();
  myItemsListAdapter1 = new ItemsListAdapter(this, items1);
  myItemsListAdapter2 = new ItemsListAdapter(this, items2);
  listView1.setAdapter(myItemsListAdapter1);
  listView2.setAdapter(myItemsListAdapter2);

  listView1.setOnItemClickListener(listOnItemClickListener);
  listView2.setOnItemClickListener(listOnItemClickListener);

    listView1.setOnItemLongClickListener(new OnItemLongClickListener(){

   @Override
   public boolean onItemLongClick(AdapterView<?> parent, View view,
     int position, long id) {
   Item selectedItem = (Item)(parent.getItemAtPosition(position));

    ItemsListAdapter associatedAdapter = (ItemsListAdapter)        (parent.getAdapter());
    List<Item> associatedList = associatedAdapter.getList();
    Item associatedItem = associatedList.get(position);
    if(removeItemToList(associatedList, associatedItem)){

     view.invalidate();
     associatedAdapter.notifyDataSetChanged();

     ItemsListAdapter list2Adapter = (ItemsListAdapter)      (listView2.getAdapter());
     List<Item> list2List = list2Adapter.getList();

      addItemToList(list2List, selectedItem);
     list2Adapter.notifyDataSetChanged();
     }

     return true;
     }});

   }

  OnItemClickListener listOnItemClickListener = new OnItemClickListener(){

  @Override
    public void onItemClick(AdapterView<?> parent, View view, int position,
    long id) {
   Toast.makeText(MainActivity.this, 
     ((Item)(parent.getItemAtPosition(position))).ItemString, 
     Toast.LENGTH_SHORT).show();
    }

 };

 private void initItems(){
  items1 = new ArrayList<Item>();
  items2 = new ArrayList<Item>();

  TypedArray arrayDrawable =     getResources().obtainTypedArray(R.array.resicon);
   TypedArray arrayText = getResources().obtainTypedArray(R.array.restext);

 for(int i=0; i<arrayDrawable.length(); i++){
  Drawable d = arrayDrawable.getDrawable(i);
   String s = arrayText.getString(i);
   Item item = new Item(d, s);
   items1.add(item);
 }

  arrayDrawable.recycle();
  arrayText.recycle();
 }

 private boolean removeItemToList(List<Item> l, Item it){
  boolean result = l.remove(it);
  return result;
  }

 private boolean addItemToList(List<Item> l, Item it){
  boolean result = l.add(it);
  return result;
 }

}    

修改activity_main.xml，使其拥有两个ListView。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="4dp"
    tools:context="com.example.androidimageviewlist.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        android:background="@android:color/background_dark" >

        <LinearLayout
            android:id="@+id/pane1"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:layout_margin="4dp"
            android:background="@android:color/background_light"
            android:orientation="vertical" >

            <ListView
                android:id="@+id/listview1"
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />
        </LinearLayout>

        <LinearLayout
            android:id="@+id/pane2"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:layout_margin="4dp"
            android:background="@android:color/background_light"
            android:orientation="vertical" >

            <ListView
                android:id="@+id/listview2"
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />
        </LinearLayout>
    </LinearLayout>

</LinearLayout>