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Android ListView实现下拉加载功能

时间：2022-06-25 23:22:58 编辑：袖梨 来源：一聚教程网

1、MyListView.Java 

public class MyListView extends ListView implements OnScrollListener {
  
 private final static int RELEASE_To_REFRESH = 0;// 下拉过程的状态值
 private final static int PULL_To_REFRESH = 1; // 从下拉返回到不刷新的状态值
 private final static int REFRESHING = 2;// 正在刷新的状态值
 private final static int DONE = 3;
 private final static int LOADING = 4;
  
 // 实际的padding的距离与界面上偏移距离的比例
 private final static int RATIO = 3;
 private LayoutInflater inflater;
  
 // ListView头部下拉刷新的布局
 private LinearLayout headerView;
 private TextView lvHeaderTipsTv;
 private TextView lvHeaderLastUpdatedTv;
 private ImageView lvHeaderArrowIv;
 private ProgressBar lvHeaderProgressBar;
  
 // 定义头部下拉刷新的布局的高度
 private int headerContentHeight;
  
 private RotateAnimation animation;
 private RotateAnimation reverseAnimation;
  
 private int startY;
 private int state;
 private boolean isBack;
  
 // 用于保证startY的值在一个完整的touch事件中只被记录一次
 private boolean isRecored;
  
 private OnRefreshListener refreshListener;
  
 private boolean isRefreshable;
  
 public MyListView(Context context) {
  super(context);
  init(context);
 }
  
 public MyListView(Context context, AttributeSet attrs) {
  super(context, attrs);
  init(context);
 }
  
 private void init(Context context) {
  inflater = LayoutInflater.from(context);
  headerView = (LinearLayout) inflater.inflate(R.layout.lv_header, null);
  lvHeaderTipsTv = (TextView) headerView
    .findViewById(R.id.lvHeaderTipsTv);
  lvHeaderLastUpdatedTv = (TextView) headerView
    .findViewById(R.id.lvHeaderLastUpdatedTv);
  
  lvHeaderArrowIv = (ImageView) headerView
    .findViewById(R.id.lvHeaderArrowIv);
  // 设置下拉刷新图标的最小高度和宽度
  lvHeaderArrowIv.setMinimumWidth(70);
  lvHeaderArrowIv.setMinimumHeight(50);
  
  lvHeaderProgressBar = (ProgressBar) headerView
    .findViewById(R.id.lvHeaderProgressBar);
  measureView(headerView);
  headerContentHeight = headerView.getMeasuredHeight();
  // 设置内边距，正好距离顶部为一个负的整个布局的高度，正好把头部隐藏
  headerView.setPadding(0, -1 * headerContentHeight, 0, 0);
  // 重绘一下
  headerView.invalidate();
  // 将下拉刷新的布局加入ListView的顶部
  addHeaderView(headerView, null, false);
  // 设置滚动监听事件
  setOnScrollListener(this);
  
  // 设置旋转动画事件
  animation = new RotateAnimation(0, -180,
    RotateAnimation.RELATIVE_TO_SELF, 0.5f,
    RotateAnimation.RELATIVE_TO_SELF, 0.5f);
  animation.setInterpolator(new LinearInterpolator());
  animation.setDuration(250);
  animation.setFillAfter(true);
  
  reverseAnimation = new RotateAnimation(-180, 0,
    RotateAnimation.RELATIVE_TO_SELF, 0.5f,
    RotateAnimation.RELATIVE_TO_SELF, 0.5f);
  reverseAnimation.setInterpolator(new LinearInterpolator());
  reverseAnimation.setDuration(200);
  reverseAnimation.setFillAfter(true);
  
  // 一开始的状态就是下拉刷新完的状态，所以为DONE
  state = DONE;
  // 是否正在刷新
  isRefreshable = false;
 }
  
 @Override
 public void onScrollStateChanged(AbsListView view, int scrollState) {
  
 }
  
 @Override
 public void onScroll(AbsListView view, int firstVisibleItem,
   int visibleItemCount, int totalItemCount) {
  if (firstVisibleItem == 0) {
   isRefreshable = true;
  } else {
   isRefreshable = false;
  }
 }
  
 @Override
 public boolean onTouchEvent(MotionEvent ev) {
  if (isRefreshable) {
   switch (ev.getAction()) {
   case MotionEvent.ACTION_DOWN:
    if (!isRecored) {
     isRecored = true;
     startY = (int) ev.getY();// 手指按下时记录当前位置
    }
    break;
   case MotionEvent.ACTION_UP:
    if (state != REFRESHING && state != LOADING) {
     if (state == PULL_To_REFRESH) {
      state = DONE;
      changeHeaderViewByState();
     }
     if (state == RELEASE_To_REFRESH) {
      state = REFRESHING;
      changeHeaderViewByState();
      onLvRefresh();
     }
    }
    isRecored = false;
    isBack = false;
  
    break;
  
   case MotionEvent.ACTION_MOVE:
    int tempY = (int) ev.getY();
    if (!isRecored) {
     isRecored = true;
     startY = tempY;
    }
    if (state != REFRESHING && isRecored && state != LOADING) {
     // 保证在设置padding的过程中，当前的位置一直是在head，否则如果当列表超出屏幕的话，当在上推的时候，列表会同时进行滚动
     // 可以松手去刷新了
     if (state == RELEASE_To_REFRESH) {
      setSelection(0);
      // 往上推了，推到了屏幕足够掩盖head的程度，但是还没有推到全部掩盖的地步
      if (((tempY - startY) / RATIO < headerContentHeight)// 由松开刷新状态转变到下拉刷新状态
        && (tempY - startY) > 0) {
       state = PULL_To_REFRESH;
       changeHeaderViewByState();
      }
      // 一下子推到顶了
      else if (tempY - startY <= 0) {// 由松开刷新状态转变到done状态
       state = DONE;
       changeHeaderViewByState();
      }
     }
     // 还没有到达显示松开刷新的时候,DONE或者是PULL_To_REFRESH状态
     if (state == PULL_To_REFRESH) {
      setSelection(0);
      // 下拉到可以进入RELEASE_TO_REFRESH的状态
      if ((tempY - startY) / RATIO >= headerContentHeight) {// 由done或者下拉刷新状态转变到松开刷新
       state = RELEASE_To_REFRESH;
       isBack = true;
       changeHeaderViewByState();
      }
      // 上推到顶了
      else if (tempY - startY <= 0) {// 由DOne或者下拉刷新状态转变到done状态
       state = DONE;
       changeHeaderViewByState();
      }
     }
     // done状态下
     if (state == DONE) {
      if (tempY - startY > 0) {
       state = PULL_To_REFRESH;
       changeHeaderViewByState();
      }
     }
     // 更新headView的size
     if (state == PULL_To_REFRESH) {
      headerView.setPadding(0, -1 * headerContentHeight
        + (tempY - startY) / RATIO, 0, 0);
  
     }
     // 更新headView的paddingTop
     if (state == RELEASE_To_REFRESH) {
      headerView.setPadding(0, (tempY - startY) / RATIO
        - headerContentHeight, 0, 0);
     }
  
    }
    break;
  
   default:
    break;
   }
  }
  return super.onTouchEvent(ev);
 }
  
 // 当状态改变时候，调用该方法，以更新界面
 private void changeHeaderViewByState() {
  switch (state) {
  case RELEASE_To_REFRESH:
   lvHeaderArrowIv.setVisibility(View.VISIBLE);
   lvHeaderProgressBar.setVisibility(View.GONE);
   lvHeaderTipsTv.setVisibility(View.VISIBLE);
   lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);
  
   lvHeaderArrowIv.clearAnimation();// 清除动画
   lvHeaderArrowIv.startAnimation(animation);// 开始动画效果
  
   lvHeaderTipsTv.setText("松开刷新");
   break;
  case PULL_To_REFRESH:
   lvHeaderProgressBar.setVisibility(View.GONE);
   lvHeaderTipsTv.setVisibility(View.VISIBLE);
   lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);
   lvHeaderArrowIv.clearAnimation();
   lvHeaderArrowIv.setVisibility(View.VISIBLE);
   // 是由RELEASE_To_REFRESH状态转变来的
   if (isBack) {
    isBack = false;
    lvHeaderArrowIv.clearAnimation();
    lvHeaderArrowIv.startAnimation(reverseAnimation);
  
    lvHeaderTipsTv.setText("下拉刷新");
   } else {
    lvHeaderTipsTv.setText("下拉刷新");
   }
   break;
  
  case REFRESHING:
  
   headerView.setPadding(0, 0, 0, 0);
  
   lvHeaderProgressBar.setVisibility(View.VISIBLE);
   lvHeaderArrowIv.clearAnimation();
   lvHeaderArrowIv.setVisibility(View.GONE);
   lvHeaderTipsTv.setText("正在刷新...");
   lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);
   break;
  case DONE:
   headerView.setPadding(0, -1 * headerContentHeight, 0, 0);
  
   lvHeaderProgressBar.setVisibility(View.GONE);
   lvHeaderArrowIv.clearAnimation();
   lvHeaderArrowIv.setImageResource(R.drawable.arrow);
   lvHeaderTipsTv.setText("下拉刷新");
   lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);
   break;
  }
 }
  
 // 此方法直接照搬自网络上的一个下拉刷新的demo，此处是“估计”headView的width以及height
 private void measureView(View child) {
  ViewGroup.LayoutParams params = child.getLayoutParams();
  if (params == null) {
   params = new ViewGroup.LayoutParams(
     ViewGroup.LayoutParams.FILL_PARENT,
     ViewGroup.LayoutParams.WRAP_CONTENT);
  }
  int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0,
    params.width);
  int lpHeight = params.height;
  int childHeightSpec;
  if (lpHeight > 0) {
   childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,
     MeasureSpec.EXACTLY);
  } else {
   childHeightSpec = MeasureSpec.makeMeasureSpec(0,
     MeasureSpec.UNSPECIFIED);
  }
  child.measure(childWidthSpec, childHeightSpec);
 }
  
 public void setonRefreshListener(OnRefreshListener refreshListener) {
  this.refreshListener = refreshListener;
  isRefreshable = true;
 }
  
 public interface OnRefreshListener {
  public void onRefresh();
 }
  
 public void onRefreshComplete() {
  state = DONE;
  lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString());
  changeHeaderViewByState();
 }
  
 private void onLvRefresh() {
  if (refreshListener != null) {
   refreshListener.onRefresh();
  }
 }
  
 public void setAdapter(LvAdapter adapter) {
  lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString());
  super.setAdapter(adapter);
 }
  
}

2、MainActivity.java 

public class MainActivity extends Activity {
 private List list;
 private MyListView lv;
 private LvAdapter adapter;
  
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  lv = (MyListView) findViewById(R.id.lv);
  list = new ArrayList();
  list.add("loonggg");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  list.add("我们都是开发者");
  adapter = new LvAdapter(list, this);
  lv.setAdapter(adapter);
  
  lv.setonRefreshListener(new OnRefreshListener() {
  
   @Override
   public void onRefresh() {
    new AsyncTask() {
     protected Void doInBackground(Void... params) {
      try {
       Thread.sleep(1000);
      } catch (Exception e) {
       e.printStackTrace();
      }
      list.add("刷新后添加的内容");
      return null;
     }
  
     @Override
     protected void onPostExecute(Void result) {
      adapter.notifyDataSetChanged();
      lv.onRefreshComplete();
     }
    }.execute(null, null, null);
   }
  });
 }
}

3、LvAdapter
public class LvAdap 
public class LvAdapter extends BaseAdapter { 
    private List list; 
    private Context context; 
 
    public LvAdapter(List list, Context context) { 
        this.list = list; 
        this.context = context; 
    } 
 
    @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) { 
        TextView tv = new TextView(context.getApplicationContext()); 
        tv.setText(list.get(position)); 
        return tv; 
    } 
 
} 

4、lv_header.xml
[html] view plain copy
 
 
     
 
     
 
         
 
         
 
             
 
             
 
             
 
             
         
 
         
 
         
 
             
 
             
 
             
 
             
         
     
 
 

5、main.xml
[html] view plain copy

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