Android:ListView

《第一行代码》第三章的练习和总结。

建立Word类

public class Word {
    private String name;
    private String info;
    public Word(String name, String info){
        this.name = name;
        this.info = info;
    }
    public String getName(){
        return name;
    }
    public String getInfo(){
        return info;
    }
}

为ListView的子项指定自定义布局。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <Button
        android:id="@+id/word_info"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="30dp"/>
    <TextView
        android:id="@+id/word_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"/>

</LinearLayout>

创建自定义适配器，继承自ArrayAdapter，泛型指定Word类。

public class WordAdapter extends ArrayAdapter<Word> {
    private int resourceID;
    public WordAdapter(Context context, int textViewResourceID, List<Word> words){
        super(context,textViewResourceID,words);
        resourceID=textViewResourceID;
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        final Word word = getItem(position);
        final View view;
        ViewHolder viewHolder;
        //对getView进行判断，如果convertView为null，则使用LayoutInflator加载布局，如果不为null则直接对convertView进行重用。 
        if(convertView ==null){

            //LayoutInflater的inflate()方法的三个参数（布局文件的ID，父布局，false代表layout属性生效，但不会为View添加父布局） 
            view = LayoutInflater.from(getContext()).inflate(resourceID,parent,false);

            viewHolder = new ViewHolder();
            viewHolder.wordName = view.findViewById(R.id.word_name);
            viewHolder.wordInfo = view.findViewById(R.id.word_info);
            //将ViewHolder储存在View中 
            view.setTag(viewHolder);
        }else{
            view = convertView;
            //重新获取ViewHolder 
            viewHolder = (ViewHolder) view.getTag();
        }
        viewHolder.wordName.setText(word.getName());
        viewHolder.wordInfo.setText(word.getName());
        viewHolder.wordInfo.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(view.getContext(), word.getInfo(), Toast.LENGTH_SHORT).show();
            }
        });
        /*TextView wordName = view.findViewById(R.id.word_name);
        Button wordInfo = view.findViewById(R.id.word_info);
        wordName.setText(word.getName());
        wordInfo.setText(word.getName());
        wordInfo.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(view.getContext(), word.getInfo(), Toast.LENGTH_SHORT).show();
            }
        });*/
        return view;
    }
    //建立ViewHolder用于对控件的实例进行缓存，当convertView为null，创建ViewHolder对象并将控件实例存放在ViewHolder中，再调用setTag()方法储存ViewHolder到View中。以便之后取出，即无需再通过findViewById()的方式来获取控件实例。
    class ViewHolder{
        TextView wordName;
        Button wordInfo;
    }
}

Activity中的内容

public class FourthActivity extends BasicActivity implements View.OnClickListener {
    private ProgressBar progressBar;
    private String[] fruitList = {"Apple","Banana","Cherry","Durian","Fig","Grape"};
    private List<word> wordList = new ArrayList<>();
    public static void actionStart(Context context){
        Intent intent = new Intent(context,FourthActivity.class);
        context.startActivity(intent);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fourth);
        ListView listView1 =findViewById(R.id.listView1);
        ListView listView2 =findViewById(R.id.listView2);
        initWords();
        WordAdapter wordAdapter = new WordAdapter(FourthActivity.this,R.layout.word_item,wordList);
        final ArrayAdapter fruitAdapter = new ArrayAdapter<string>(FourthActivity.this,android.R.layout.simple_list_item_1,fruitList);
        listView1.setAdapter(wordAdapter);
        listView2.setAdapter(fruitAdapter);
        listView2.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView parent, View view, int position, long id) {
                Toast.makeText(FourthActivity.this,fruitList[position],Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void initWords(){
        Word a = new Word("AAA","This is word A.");
        wordList.add(a);
        Word b = new Word("BBB","This is word B.");
        wordList.add(b);
        Word c = new Word("CCC","This is word C.");
        wordList.add(c);
        Word d = new Word("DDD","This is word D.");
        wordList.add(d);
        Word e = new Word("EEE","This is word E.");
        wordList.add(e);
        Word f = new Word("FFF","This is word F.");
        wordList.add(f);
        Word g = new Word("GGG","This is word G.");
        wordList.add(g);
        Word h = new Word("HHH","This is word H.");
        wordList.add(h);
        Word i = new Word("III","This is word I.");
        wordList.add(i);
        Word j = new Word("JJJ","This is word J.");
        wordList.add(j);
    }
}</string></word>

实现了两个ListView，上半部分为带Button自定义布局，下部分实现了setOnItemClickListener为ListView注册了监听器。

但是注意到，如果给上半部分实现了自定义布局的ListView添加setOnItemClickListener，点击自定义布局中的Button就无效，想让Button能够被点击，具体实现较为麻烦，而RecyclerView直接摈弃了点击事件的监听器，点击事件由具体View注册，避免了这个问题。