ListView :当我们需要有大量的数据信息进行显示时，这时就需要用到ListView。那么如何使用它呢？
简单使用：
1、在布局文件中创建ListView控件并设置相关属性id如：easy_list_view。
2、在activity中创建Adapter,Listview和一个数组对象。
private Integer[] data = new Integer[200];for (int i = 0;i<200;i++) {
data[i] = i;
}
ArrayAdapter<Integer> adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, data);
ListView listView = (ListView) findViewById(R.id.easy_list_view);
listView.setAdapter(adapter);总结：这样的listView特别简单只是单纯的用了sdk原生的东西。但我们一般用到的数据都不会是一组数据就一个信息，肯定是有图有文字甚至很多复杂的控件。所以下面的是重点学习的。
自定义ListView:
我把我们接下来要作的事罗列一下：
1、创建自定义布局（list一行的布局）。
2、创建创建数据Bean类（这里是我的一个自称：可以理解为一个数据类）。
public class Fruit {
Fruit(String name, int imageId) {
this.name = name;
this.imageId = imageId;
}
public String getName() {
return name;
}
public int getImageId() {
return imageId;
}
private String name = "1";
private int imageId = R.drawable.one;
}3、自定义一个Adapter继承的Adapter看情况，我这里是Array。
/*
* 继承ArrayAdapter自定义Adapter
* 且是通过convertView与ViewHolder共同优化的一个自定义adapter。
* 用setTag与getTag方法达到ViewHolder的重用。
* */
public class FruitAdapter extends ArrayAdapter<Fruit> {
// 此为自定义的布局
private int resourceId;
// 构造方法。获取自定义布局
FruitAdapter(@NonNull Context context, int resource, @NonNull List<Fruit> fruits) {
super(context, resource, fruits);
resourceId = resource;
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
Fruit fruit = getItem(position);//获取当前项的fruit实例
View view;
ViewHolder viewHolder;
//重用
if (convertView == null) {
view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);//加载布局
viewHolder = new ViewHolder();
viewHolder.fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
viewHolder.fruitName = (TextView) view.findViewById(R.id.fruit_name);
view.setTag(viewHolder);
}else{
view = convertView;
viewHolder = (ViewHolder) view.getTag();
}
assert fruit != null;
viewHolder.fruitImage.setImageResource(fruit.getImageId());
viewHolder.fruitName .setText(fruit.getName());
return view;
}
class ViewHolder{
ImageView fruitImage;
TextView fruitName;
}
}4、在activity使用它们；
public class DefineListViewActivity extends AppCompatActivity {
private List<Fruit> fruitList = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_define_list_view);
//循环多遍历一点
for (int i = 0; i < 10; i++)
initFruits();
FruitAdapter adapter = new FruitAdapter(this, R.layout.define_list_view_fruit, fruitList);
ListView listView = (ListView) findViewById(R.id.define_list_view);
listView.setAdapter(adapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Fruit fruit = fruitList.get(position);
Toast.makeText(DefineListViewActivity.this, fruit.getName(), Toast.LENGTH_SHORT).show();
}
});
}
private void initFruits() {
Fruit one = new Fruit("one", R.drawable.one);
Fruit two = new Fruit("two", R.drawable.two);
Fruit three = new Fruit("three", R.drawable.three);
Fruit four = new Fruit("four", R.drawable.four);
Fruit five = new Fruit("five", R.drawable.five);
Fruit six = new Fruit("six", R.drawable.six);
Fruit seven = new Fruit("seven", R.drawable.seven);
fruitList.add(one);
fruitList.add(two);
fruitList.add(three);
fruitList.add(four);
fruitList.add(five);
fruitList.add(six);
fruitList.add(seven);
}
}更强大的滚动控件RecyclerView：
相比较而言，RecyclerView的性能及功能比ListView更强大，所以现在我们更应该去学习这个控件。
1、由于这个是新加的所以这个是在support库中才有的所以需要依赖recyclerview这个库。
2、创建自定义布局：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:orientation="vertical"
tools:ignore="UseCompoundDrawables">
<ImageView
android:id="@+id/imageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:contentDescription="@string/picture"
app:srcCompat="@drawable/one" />
<TextView
android:id="@+id/item_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="@string/textview"
android:textSize="14sp" />
</LinearLayout>3、创建基本的数据类Fruit；
public class Fruit {
private String fruitName;
private int fruitImage;
Fruit(String fruitName,int fruitImage){
this.fruitName = fruitName;
this.fruitImage = fruitImage;
}
public String getFruitName() {
return fruitName;
}
public int getFruitImage() {
return fruitImage;
}
}
4、创建自定义Adapter注意：继承RecyclerView.Adapter<类.ViewHolder>其中ViewHolder这是个内部类且继承了RecyclerView.ViewHolder。
public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {
// 水果数据
private List<Fruit> fruits;
// 在构造时获取水果数据
FruitAdapter(List<Fruit> fruits) {
this.fruits = fruits;
}
// 加载布局并创建实例ViewHolder
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item,parent,false);
return new ViewHolder(view);
}
// 把数据与子项绑定起来
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
Fruit fruit = fruits.get(position);
holder.fruitImage.setImageResource(fruit.getFruitImage());
holder.fruitName.setText(fruit.getFruitName());
}
// 获取数据的长度
@Override
public int getItemCount() {
return fruits.size();
}
// 创建静态的内部类ViewHolder并继承RecyclerView.ViewHolder
static class ViewHolder extends RecyclerView.ViewHolder {
TextView fruitName;
ImageView fruitImage;
ViewHolder(View itemView) {
super(itemView);
fruitName = (TextView) itemView.findViewById(R.id.item_name);
fruitImage = (ImageView) itemView.findViewById(R.id.imageView);
}
}
}5、在Activity中显示它们，与ListView步骤差不多，只不过多了一步LinearLayoutManager
public class MainActivity extends AppCompatActivity {
private List<Fruit> fruits=new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initfruist();
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
RecyclerView recyclerView = findViewById(R.id.reclyclerView);
recyclerView.setLayoutManager(linearLayoutManager);
FruitAdapter fruitAdapter = new FruitAdapter(fruits);
recyclerView.setAdapter(fruitAdapter);
}
private void initfruist() {
for (int i=0;i<200;i++) {
fruits.add(new Fruit("one", R.drawable.one));
fruits.add(new Fruit("two", R.drawable.two));
fruits.add(new Fruit("three", R.drawable.three));
fruits.add(new Fruit("four", R.drawable.four));
fruits.add(new Fruit("five", R.drawable.five));
fruits.add(new Fruit("six", R.drawable.six));
fruits.add(new Fruit("seven", R.drawable.seven));
}
}
}其实RecycleView还是挺简单的逻辑上易于理解，只要上代码两三遍基本就也就稍微会用了。
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