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自定义ViewGroup 实现拖动跟快速滚动的效果

犹大之窗 2023-03-20 阅读 53
androidideRESTHarmonyOS后端开发


  之前做到个项目要类似listView或者GridView中的控件移动的效果（主屏上所有程序列表上的效果）：
1：子控件跟着手指移动
2：快速拨动一下，根据拨动的速度 滑动过去
3：拖过头，放手后弹回去

   但是用listView或者GridView又不好实现项目要求的其他效果..于是继承viewGroup实现以上效果。

   既然要获取拨动速度，并以此滑动。首先想到了OnGestureListener 这个接口，实现这个接口并实现其onFling方法.

  还要控制拖动。重写onTouchEvent方法，并在其中控制内容控件的拖动，反弹等效果

这时候基本已经完成了。。。。测试了一下了，发现了一个问题，当手指点在viewGroup上

进行 拖动是没问题的，但是在子控件上就不行了，这是事件响应的问题 那么还要做如面的处

理:实现onInterceptTouchEvent方法，判断是拖动事件时 ，将事件传递下去。 

import java.util.List;
import android.content.Context;
import android.graphics.Color;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.GestureDetector.OnGestureListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Scroller;
import android.widget.Toast;
import android.widget.ImageView.ScaleType;

public class MyViewGroup extends ViewGroup implements OnGestureListener {

  private float mLastMotionY;// 最后点击的点
  private GestureDetector detector;
  int move = 0;// 移动距离
  int MAXMOVE = 850;// 最大允许的移动距离
  private Scroller mScroller;
  int up_excess_move = 0;// 往上多移的距离
  int down_excess_move = 0;// 往下多移的距离
  private final static int TOUCH_STATE_REST = 0;
  private final static int TOUCH_STATE_SCROLLING = 1;
  private int mTouchSlop;
  private int mTouchState = TOUCH_STATE_REST;
  Context mContext;
  

  public MyViewGroup(Context context) {
    super(context);
    mContext = context;
    // TODO Auto-generated constructor stub
    setBackgroundResource(R.drawable.pic);
    mScroller = new Scroller(context);
    detector = new GestureDetector(this);

    final ViewConfiguration configuration = ViewConfiguration.get(context);
    // 获得可以认为是滚动的距离
    mTouchSlop = configuration.getScaledTouchSlop();

    // 添加子View
    for (int i = 0; i < 48; i++) {
      final Button  MButton = new Button(context);
      MButton.setText("" + (i + 1));
      MButton.setOnClickListener(new OnClickListener() {
        
        public void onClick(View v) {
          // TODO Auto-generated method stub
          Toast.makeText(mContext, MButton.getText(), Toast.LENGTH_SHORT).show(); 
        }
      });
      addView(MButton);
    }
  }

  @Override
  public void computeScroll() {
    if (mScroller.computeScrollOffset()) {
      // 返回当前滚动X方向的偏移
      scrollTo(0, mScroller.getCurrY());
      postInvalidate();
    }
  }

  @Override
  public boolean onInterceptTouchEvent(MotionEvent ev) {
    final int action = ev.getAction();

    final float y = ev.getY();
    switch (ev.getAction())
    {
    case MotionEvent.ACTION_DOWN:

      mLastMotionY = y;
      mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
          : TOUCH_STATE_SCROLLING;
      break;
    case MotionEvent.ACTION_MOVE:
      final int yDiff = (int) Math.abs(y - mLastMotionY);
      boolean yMoved = yDiff > mTouchSlop;
      // 判断是否是移动
      if (yMoved) {
        mTouchState = TOUCH_STATE_SCROLLING;
      }
      break;
    case MotionEvent.ACTION_UP:
      mTouchState = TOUCH_STATE_REST;
      break;
    }
    return mTouchState != TOUCH_STATE_REST;
  }

  @Override
  public boolean onTouchEvent(MotionEvent ev) {

    // final int action = ev.getAction();

    final float y = ev.getY();
    switch (ev.getAction())
    {
    case MotionEvent.ACTION_DOWN:
      if (!mScroller.isFinished()) {
        mScroller.forceFinished(true);
        move = mScroller.getFinalY();
      }
      mLastMotionY = y;
      break;
    case MotionEvent.ACTION_MOVE:
      if (ev.getPointerCount() == 1) {
        
        // 随手指 拖动的代码
        int deltaY = 0;
        deltaY = (int) (mLastMotionY - y);
        mLastMotionY = y;
        Log.d("move", "" + move);
        if (deltaY < 0) {
          // 下移
          // 判断上移 是否滑过头
          if (up_excess_move == 0) {
            if (move > 0) {
              int move_this = Math.max(-move, deltaY);
              move = move + move_this;
              scrollBy(0, move_this);
            } else if (move == 0) {// 如果已经是最顶端 继续往下拉
              Log.d("down_excess_move", "" + down_excess_move);
              down_excess_move = down_excess_move - deltaY / 2;// 记录下多往下拉的值
              scrollBy(0, deltaY / 2);
            }
          } else if (up_excess_move > 0)// 之前有上移过头
          {         
            if (up_excess_move >= (-deltaY)) {
              up_excess_move = up_excess_move + deltaY;
              scrollBy(0, deltaY);
            } else {            
              up_excess_move = 0;
              scrollBy(0, -up_excess_move);       
            }
          }
        } else if (deltaY > 0) {
          // 上移
          if (down_excess_move == 0) {
            if (MAXMOVE - move > 0) {
              int move_this = Math.min(MAXMOVE - move, deltaY);
              move = move + move_this;
              scrollBy(0, move_this);
            } else if (MAXMOVE - move == 0) {
              if (up_excess_move <= 100) {
                up_excess_move = up_excess_move + deltaY / 2;
                scrollBy(0, deltaY / 2);
              }
            }
          } else if (down_excess_move > 0) {
            if (down_excess_move >= deltaY) {
              down_excess_move = down_excess_move - deltaY;
              scrollBy(0, deltaY);
            } else {
              down_excess_move = 0;
              scrollBy(0, down_excess_move);
            }
          }
        }   
      } 
      break;
    case MotionEvent.ACTION_UP:     
      // 多滚是负数 记录到move里
      if (up_excess_move > 0) {
        // 多滚了 要弹回去
        scrollBy(0, -up_excess_move);
        invalidate();
        up_excess_move = 0;
      }
      if (down_excess_move > 0) {
        // 多滚了 要弹回去
        scrollBy(0, down_excess_move);
        invalidate();
        down_excess_move = 0;
      }
      mTouchState = TOUCH_STATE_REST;
      break;
    }
    return this.detector.onTouchEvent(ev);
  }

  int Fling_move = 0;

  public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
      float velocityY) {
     //随手指 快速拨动的代码
    Log.d("onFling", "onFling");
    if (up_excess_move == 0 && down_excess_move == 0) {

      int slow = -(int) velocityY * 3 / 4;
      mScroller.fling(0, move, 0, slow, 0, 0, 0, MAXMOVE);
      move = mScroller.getFinalY();
      computeScroll();
    }
    return false;
  }

  public boolean onDown(MotionEvent e) {
    // TODO Auto-generated method stub
    return true;
  }

  public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
      float distanceY) {
    return false;
  }

  public void onShowPress(MotionEvent e) {
    // // TODO Auto-generated method stub
  }

  public boolean onSingleTapUp(MotionEvent e) {
    // TODO Auto-generated method stub
    return false;
  }

  public void onLongPress(MotionEvent e) {
    // TODO Auto-generated method stub
  }

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    // TODO Auto-generated method stub
    int childTop = 0;
    int childLeft = 0;
    final int count = getChildCount();
    for (int i = 0; i < count; i++) {
      final View child = getChildAt(i);
      if (child.getVisibility() != View.GONE) {
        child.setVisibility(View.VISIBLE);
        child.measure(r - l, b - t);
        child
            .layout(childLeft, childTop, childLeft + 80,
                childTop + 80);
        if (childLeft < 160) {
          childLeft += 80;
        } else {
          childLeft = 0;
          childTop += 80;
        }
      }
    }
  }

}



import android.content.Context;
import android.view.View;
import android.view.ViewGroup;

public class Workspace extends ViewGroup {

  public Workspace(Context context) {
    super(context);
    // TODO Auto-generated constructor stub
    addView(new MyViewGroup(context));
  }

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    // TODO Auto-generated method stub
    final int count = getChildCount();
    for (int i = 0; i < count; i++) {
      final View child = getChildAt(i);
      child.measure(r - l, b - t);
      child.layout(0, 0, 320, 480);
    }
  }

}



import android.app.Activity;
import android.os.Bundle;

public class MoveViewGroup extends Activity {
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(new Workspace(this));

  }
}


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