package muzhi.nestedscrollingchild;
import android.annotation.TargetApi;
import android.content.Context;
import android.os.Build;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
/**
* Created by Administrator on 2017/8/7.
*/
public class NestedChildView extends View implements NestedScrollingChild{
public static final String TAG = "NestedChildView";
private final NestedScrollingChildHelper childHelper = new NestedScrollingChildHelper(this);
private float downY;
private int[] consumed = new int[2];
private int[] offsetInWindow = new int[2];
public NestedChildView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private void init() {
setNestedScrollingEnabled(true);
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
@Override
public boolean onTouchEvent(MotionEvent event) {
final int actionMasked = MotionEventCompat.getActionMasked(event);
// 取第一个接触屏幕的手指Id
final int pointerId = MotionEventCompat.getPointerId(event, 0);
switch (actionMasked) {
case MotionEvent.ACTION_DOWN:
// 取得当前的Y，并赋值给lastY变量
downY = getPointerY(event, pointerId);
// 找不到手指，放弃掉这个触摸事件流
if (downY == -1) {
return false;
}
// 通知父View，开始滑动
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
break;
case MotionEvent.ACTION_MOVE:
// 获得当前手指的Y
final float pointerY = getPointerY(event, pointerId);
// 找不到手指，放弃掉这个触摸事件流
if (pointerY == -1) {
return false;
}
// 计算出滑动的偏移量
float deltaY = pointerY - downY;
// 通知父View, 子View想滑动 deltaY 个偏移量，父View要不要先滑一下，然后把父View滑了多少，告诉子View一下
// 下面这个方法的前两个参数为在x，y方向上想要滑动的偏移量
// 第三个参数为一个长度为2的整型数组，父View将消费掉的距离放置在这个数组里面
// 第四个参数为一个长度为2的整型数组，父View在屏幕里面的偏移量放置在这个数组里面
// 返回值为 true，代表父View有消费任何的滑动.
if (dispatchNestedPreScroll(0, (int) deltaY, consumed, offsetInWindow)) {
// 偏移量需要减掉被父View消费掉的,如果不减掉，子view和父view滑动的距离是不一样的
deltaY -= consumed[1];
}
// 上面的 (int)deltaY 会造成精度丢失，这里把精度给舍弃掉
if(Math.floor(Math.abs(deltaY)) == 0) {
deltaY = 0;
}
// 这里移动子View，下面的min,max是为了控制边界，避免子View越界
setY(Math.min(Math.max(getY() + deltaY, 0), ((View) getParent()).getHeight() - getHeight()));
break;
}
return true;
}
/**
* 这个方法通过pointerId获取pointerIndex,然后获取Y
*
*/
private float getPointerY(MotionEvent event, int pointerId) {
final int pointerIndex = MotionEventCompat.findPointerIndex(event, pointerId);
if (pointerIndex < 0) {
return -1;
}
return MotionEventCompat.getY(event, pointerIndex);
}
/**
* 设置事件分发允许
* @param enabled
*/
@Override
public void setNestedScrollingEnabled(boolean enabled) {
Log.d(TAG, String.format("setNestedScrollingEnabled , enabled = %b", enabled));
childHelper.setNestedScrollingEnabled(enabled);
}
/**
* 判断事件分发
* @return
*/
@Override
public boolean isNestedScrollingEnabled() {
Log.d(TAG, "isNestedScrollingEnabled");
return childHelper.isNestedScrollingEnabled();
}
/**
* 开始滑动前
* @param axes
* @return
*/
@Override
public boolean startNestedScroll(int axes) {
Log.d(TAG, String.format("startNestedScroll , axes = %d", axes));
return childHelper.startNestedScroll(axes);
}
/**
* 停止滑动
*/
@Override
public void stopNestedScroll() {
Log.d(TAG, "stopNestedScroll");
childHelper.stopNestedScroll();
}
/**
* 判断是否滑动父类
* @return
*/
@Override
public boolean hasNestedScrollingParent() {
Log.d(TAG, "hasNestedScrollingParent");
return childHelper.hasNestedScrollingParent();
}
/**
* 回调中获取父类消费了的距离
* @param dxConsumed
* @param dyConsumed
* @param dxUnconsumed
* @param dyUnconsumed
* @param offsetInWindow
* @return
*/
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
final boolean b = childHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
return b;
}
/**
* 也是获取值
* @param dx
* @param dy
* @param consumed
* @param offsetInWindow
* @return
*/
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
final boolean b = childHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
return b;
}
/**
* filing的时候获取
* @param velocityX
* @param velocityY
* @param consumed
* @return
*/
@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
Log.d(TAG, String.format("dispatchNestedFling , velocityX = %f, velocityY = %f, consumed = %b", velocityX, velocityY, consumed));
return childHelper.dispatchNestedFling(velocityX, velocityY, consumed);
}
@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
Log.d(TAG, String.format("dispatchNestedPreFling , velocityX = %f, velocityY = %f", velocityX, velocityY));
return childHelper.dispatchNestedPreFling(velocityX, velocityY);
}
}在父ViewGroup中
package muzhi.nestedscrollingchild;
import android.content.Context;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.NestedScrollingParent;
import android.support.v4.view.NestedScrollingParentHelper;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
/**
* Created by Administrator on 2017/8/7.
*/
public class NestedParentView extends FrameLayout implements NestedScrollingParent {
public static final String TAG = NestedParentView.class.getSimpleName();
private NestedScrollingParentHelper parentHelper;
public NestedParentView(Context context) {
super(context);
}
public NestedParentView(Context context, AttributeSet attrs) {
super(context, attrs);
parentHelper = new NestedScrollingParentHelper(this);
}
@Override
public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
Log.d(TAG, String.format("onStartNestedScroll, child = %s, target = %s, nestedScrollAxes = %d", child, target, nestedScrollAxes));
return true;
}
@Override
public void onNestedScrollAccepted(View child, View target, int nestedScrollAxes) {
Log.d(TAG, String.format("onNestedScrollAccepted, child = %s, target = %s, nestedScrollAxes = %d", child, target, nestedScrollAxes));
parentHelper.onNestedScrollAccepted(child, target, nestedScrollAxes);
}
@Override
public void onStopNestedScroll(View target) {
Log.d(TAG, "onStopNestedScroll");
parentHelper.onStopNestedScroll(target);
}
@Override
public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
Log.d(TAG, String.format("onNestedScroll, dxConsumed = %d, dyConsumed = %d, dxUnconsumed = %d, dyUnconsumed = %d", dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed));
}
@Override
public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
//dy，就是直接表示一次的偏移量，方向和坐标系的相同，而且每一次的
// 应该移动的Y距离
Log.i("onNestedPreScroll","===================");
Log.i("onNestedPreScroll","dy==="+dy);
Log.i("onNestedPreScroll","getY==="+getY());
final float shouldMoveY = getY() + dy;//表示最终停留的位置
Log.i("onNestedPreScroll","shouldMoveY==="+shouldMoveY);
// 获取到父View的容器的引用，这里假定父View容器是View
final View parent = (View) getParent();
int consumedY;
// 如果超过了父View的上边界，只消费子View到父View上边的距离
if (shouldMoveY <= 0) {
consumedY = - (int) getY();//将它移动回来
} else if (shouldMoveY >= parent.getHeight() - getHeight()) {
// 如果超过了父View的下边界，只消费子View到父View
consumedY = (int) (parent.getHeight() - getHeight() - getY());
} else {
// 其他情况下全部消费
consumedY = dy;
}
Log.i("onNestedPreScroll"," getHeight()==="+ getHeight());
Log.i("onNestedPreScroll"," parent.getHeight()==="+ parent.getHeight());
Log.i("onNestedPreScroll","consumedY==="+consumedY);
Log.i("onNestedPreScroll","===================");
// 对父View进行移动
setY(getY() + consumedY);
// 将父View消费掉的放入consumed数组中
consumed[1] = consumedY;
}
@Override
public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
Log.d(TAG, String.format("onNestedFling, velocityX = %f, velocityY = %f, consumed = %b", velocityX, velocityY, consumed));
return true;
}
@Override
public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
Log.d(TAG, String.format("onNestedPreFling, velocityX = %f, velocityY = %f", velocityX, velocityY));
return true;
}
@Override
public int getNestedScrollAxes() {
Log.d(TAG, "getNestedScrollAxes");
return parentHelper.getNestedScrollAxes();
}
}
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