- ListView的使用
- Adapter的概念及使用
- RecyclerView
- GirdView
- Spinner
RecyclerView控件
- ListView是Android中最常用的控件之一，可以通过手指上下滑动，滚动视图显示内容，用法相对其他控件比较复杂，不过它并不是完全没有缺点的，比如说如果我们不使用一些技巧来提升它的运行效率，那么ListView的性能就会非常差，还有扩展性也不够好，它只能实现数据纵向滚动效果，如果想实现横向滚动，ListView是做不到的。
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为此，Andriod提供了一个更强大的滚动控件——RecyclerView，它可以说是一个增强版的ListVIew,不仅可以轻松实现和它一样的效果，还优化了它各种不足之处，目前官方更推荐使用RecyclerView！
首先让Android Studio自动帮我们创建好活动
*想要使用这个控件，首先需要在项目的build.gradle中添加相应的依赖库才行
image.png
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然后修改fragement_recycler_view.xml中的代码
image.png - 接下来为RecyclerView准备一个适配器，新建RecyclerViewAdapter类，让适配器继承自RecyclerView.Adapter，并将泛型指定RecyclerViewAdapter.ViewHolder。代码如下：
public class RecyclerViewAdapter<V extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {
private List<Exercise> exercises;
static class ViewHolder extends RecyclerView.ViewHolder{
TextView tvtvOder,tvTitle,tvSubTitle;
public ViewHolder(View view){
super(view);
tvtvOder= view.findViewById(R.id.tv_order);
tvTitle= view.findViewById(R.id.tv_title);
tvSubTitle= view.findViewById(R.id.tv_sub_title);
}
}
public RecyclerViewAdapter(List<Exercise> exerList){
exercises=exerList;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.item_exercise , parent ,false);
ViewHolder holder = new ViewHolder(view);
//设置Item点击的监听器
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
}
});
return holder;
}
@Override
public void onBindViewHolder(@NonNull final ViewHolder holder, final int position) {
Exercise exercise= exercises.get(position);
holder.tvTitle.setText(exercise.getTitle());
holder.tvtvOder.setText(String.valueOf(position+1));
holder.tvSubTitle.setText(exercise.getSubTitle());
// //设置圆角背景的颜色
// GradientDrawable drawable=(GradientDrawable) holder.tvtvOder.getBackground();
// drawable.setColor(Color.parseColor(exercise.getBgColor()));
//设置监听
if(itemClickLisrener != null){
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
itemClickLisrener.onItemClick(holder.itemView,position);
}
});
holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
itemClickLisrener.onItemLongClick(holder.itemView,position);
return true;
}
});
}
}
private OnItemClickLisrener itemClickLisrener;
public void setOnItemClickListener(OnItemClickLisrener listener){
this.itemClickLisrener=listener;
}
//回调事件的接口
public interface OnItemClickLisrener{
void onItemClick(View view,int position);
void onItemLongClick(View view,int positon);
}
@Override
public int getItemCount() {
return exercises.size();
}
}
- 适配器准备好以后，我们就开始使用RecyclerView了，修改代码如下图：
public class ExerciseDetailActivity extends AppCompatActivity implements ExerciseDetailAdapter.OnSelectListener {
private int id;
private String title;
private List<ExerciseDetail> details;
private RecyclerView lvDetails;
private ExerciseDetailAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_recycler_view);
initData();
initView();
}
public void initData(){
id =getIntent().getIntExtra("id",0);
title=getIntent().getStringExtra("title");
details=new ArrayList<>();
try{
InputStream is=getResources().getAssets().open("chapter"+id+".xml");
details= IOUtils.getXmlContents(is);
is.close();
}catch (Exception e){
e.printStackTrace();
}
}
public void initView(){
lvDetails=findViewById(R.id.recycle_view);
LinearLayoutManager manager=new LinearLayoutManager(this);
lvDetails.setLayoutManager(manager);
adapter=new ExerciseDetailAdapter(details,this);
lvDetails.setAdapter(adapter);
//增加标题
// TextView title=new TextView(this);
// title.setTextColor(Color.parseColor("#000000"));
// title.setText("一，选择题");
// title.setPadding(10,15,0,0);
// lvExercises.addHeaderView(title);
}
public void onSelectA(int position, ImageView ivA,ImageView ivB,ImageView ivC,ImageView ivD){
ExerciseDetail detail=details.get(position);
if(detail.getAnswer() !=1){
detail.setSelect(1);
}else{
detail.setSelect(0);
}
switch (detail.getAnswer()){
case 1:
ivA.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 2:
ivB.setImageResource(R.drawable.ic_exercise_answer_error);
ivA.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 3:
ivC.setImageResource(R.drawable.ic_exercise_answer_error);
ivA.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 4:
ivD.setImageResource(R.drawable.ic_exercise_answer_error);
ivA.setImageResource(R.drawable.ic_exercise_answer_right);
break;
}
}
@Override
public void onSelectB(int position, ImageView ivA, ImageView ivB, ImageView ivC, ImageView ivD) {
ExerciseDetail detail=details.get(position);
if(detail.getAnswer() !=2){
detail.setSelect(2);
}else{
detail.setSelect(0);
}
switch (detail.getAnswer()){
case 1:
ivA.setImageResource(R.drawable.ic_exercise_answer_error);
ivB.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 2:
ivB.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 3:
ivC.setImageResource(R.drawable.ic_exercise_answer_error);
ivB.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 4:
ivD.setImageResource(R.drawable.ic_exercise_answer_error);
ivB.setImageResource(R.drawable.ic_exercise_answer_right);
break;
}
}
@Override
public void onSelectC(int position, ImageView ivA, ImageView ivB, ImageView ivC, ImageView ivD) {
ExerciseDetail detail=details.get(position);
if(detail.getAnswer() !=3){
detail.setSelect(3);
}else{
detail.setSelect(0);
}
switch (detail.getAnswer()){
case 1:
ivA.setImageResource(R.drawable.ic_exercise_answer_right);
ivB.setImageResource(R.drawable.ic_exercise_answer_error);
break;
case 2:
ivA.setImageResource(R.drawable.ic_exercise_answer_error);
ivC.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 3:
ivC.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 4:
ivD.setImageResource(R.drawable.ic_exercise_answer_error);
ivC.setImageResource(R.drawable.ic_exercise_answer_right);
break;
}
}
@Override
public void onSelectD(int position, ImageView ivA, ImageView ivB, ImageView ivC, ImageView ivD) {
ExerciseDetail detail=details.get(position);
if(detail.getAnswer() !=4){
detail.setSelect(4);
}else{
detail.setSelect(0);
}
switch (detail.getAnswer()){
case 1:
ivA.setImageResource(R.drawable.ic_exercise_answer_error);
ivD.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 2:
ivA.setImageResource(R.drawable.ic_exercise_answer_error);
ivD.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 3:
ivB.setImageResource(R.drawable.ic_exercise_answer_error);
ivD.setImageResource(R.drawable.ic_exercise_answer_right);
break;
case 4:
ivD.setImageResource(R.drawable.ic_exercise_answer_right);
break;
}
}
}
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现在可以运行一下程序了，效果如图：
ListView运行效果.png - 可以看到，RecyclerView实现了和ListView几乎一模一样的效果，虽然代码量没有减少，但是逻辑上清晰了很多，RecyclerView还可以实现横向滚动和瀑布流布局哦，在后面的课程中会学习到GirdView。
