自定义ViewGroup 实现拖动跟快速滚动的效果

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。

[java] view
plaincopy

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;

}

}

}

}

}

[java] view
plaincopy

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);

}

}

}

[java] view
plaincopy

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));

}

}