Andoird 自定义ViewGroup实现竖向引导界面
来源:互联网 发布:linux max map count 编辑:程序博客网 时间:2024/05/29 03:17
原文地址:http://blog.csdn.net/lmj623565791/article/details/23692439
一般进入APP都有欢迎界面,基本都是水平滚动的,今天和大家分享一个垂直滚动的例子。
先来看看效果把:
1、首先是布局文件:
- <com.example.verticallinearlayout.VerticalLinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
- xmlns:tools="http://schemas.android.com/tools"
- android:id="@+id/id_main_ly"
- android:layout_width="match_parent"
- android:layout_height="fill_parent"
- android:orientation="vertical"
- android:background="#fff" >
-
- <RelativeLayout
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:background="@drawable/w02" >
-
- <Button
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:text="hello" />
- </RelativeLayout>
-
- <RelativeLayout
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:background="@drawable/w03" >
-
- <Button
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:layout_centerInParent="true"
- android:background="#fff"
- android:text="hello" />
- </RelativeLayout>
-
- <RelativeLayout
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:background="@drawable/w04" >
-
- <Button
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:layout_centerInParent="true"
- android:text="hello" />
- </RelativeLayout>
-
- <RelativeLayout
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:background="@drawable/w05" >
-
- <Button
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:layout_centerInParent="true"
- android:text="hello" />
- </RelativeLayout>
-
- </com.example.verticallinearlayout.VerticalLinearLayout>
在自定义的ViewGroup中放入了4个RelativeLayout,每个RelativeLayout都设置了背景图片,背景图片来自微信~2、主要看自定义的Layout了
- package com.example.verticallinearlayout;
-
- import android.content.Context;
- import android.util.AttributeSet;
- import android.util.DisplayMetrics;
- import android.util.Log;
- import android.view.MotionEvent;
- import android.view.VelocityTracker;
- import android.view.View;
- import android.view.ViewGroup;
- import android.view.WindowManager;
- import android.widget.Scroller;
-
- public class VerticalLinearLayout extends ViewGroup
- {
-
-
-
- private int mScreenHeight;
-
-
-
- private int mScrollStart;
-
-
-
- private int mScrollEnd;
-
-
-
- private int mLastY;
-
-
-
- private Scroller mScroller;
-
-
-
- private boolean isScrolling;
-
-
-
- private VelocityTracker mVelocityTracker;
-
-
-
- private int currentPage = 0;
-
- private OnPageChangeListener mOnPageChangeListener;
-
- public VerticalLinearLayout(Context context, AttributeSet attrs)
- {
- super(context, attrs);
-
-
-
-
- WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
- DisplayMetrics outMetrics = new DisplayMetrics();
- wm.getDefaultDisplay().getMetrics(outMetrics);
- mScreenHeight = outMetrics.heightPixels;
-
- mScroller = new Scroller(context);
- }
-
- @Override
- protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
- {
- super.onMeasure(widthMeasureSpec, heightMeasureSpec);
- int count = getChildCount();
- for (int i = 0; i < count; ++i)
- {
- View childView = getChildAt(i);
- measureChild(childView, widthMeasureSpec,mScreenHeight);
- }
- }
-
- @Override
- protected void onLayout(boolean changed, int l, int t, int r, int b)
- {
- if (changed)
- {
- int childCount = getChildCount();
-
- MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();
- lp.height = mScreenHeight * childCount;
- setLayoutParams(lp);
-
- for (int i = 0; i < childCount; i++)
- {
- View child = getChildAt(i);
- if (child.getVisibility() != View.GONE)
- {
- child.layout(l, i * mScreenHeight, r, (i + 1) * mScreenHeight);
- }
- }
-
- }
-
- }
-
- @Override
- public boolean onTouchEvent(MotionEvent event)
- {
-
- if (isScrolling)
- return super.onTouchEvent(event);
-
- int action = event.getAction();
- int y = (int) event.getY();
-
- obtainVelocity(event);
- switch (action)
- {
- case MotionEvent.ACTION_DOWN:
-
- mScrollStart = getScrollY();
- mLastY = y;
- break;
- case MotionEvent.ACTION_MOVE:
-
- if (!mScroller.isFinished())
- {
- mScroller.abortAnimation();
- }
-
- int dy = mLastY - y;
-
- int scrollY = getScrollY();
-
- if (dy < 0 && scrollY + dy < 0)
- {
- dy = -scrollY;
- }
-
- if (dy > 0 && scrollY + dy > getHeight() - mScreenHeight)
- {
- dy = getHeight() - mScreenHeight - scrollY;
- }
-
- scrollBy(0, dy);
- mLastY = y;
- break;
- case MotionEvent.ACTION_UP:
-
- mScrollEnd = getScrollY();
-
- int dScrollY = mScrollEnd - mScrollStart;
-
- if (wantScrollToNext())
- {
- if (shouldScrollToNext())
- {
- mScroller.startScroll(0, getScrollY(), 0, mScreenHeight - dScrollY);
-
- } else
- {
- mScroller.startScroll(0, getScrollY(), 0, -dScrollY);
- }
-
- }
-
- if (wantScrollToPre())
- {
- if (shouldScrollToPre())
- {
- mScroller.startScroll(0, getScrollY(), 0, -mScreenHeight - dScrollY);
-
- } else
- {
- mScroller.startScroll(0, getScrollY(), 0, -dScrollY);
- }
- }
- isScrolling = true;
- postInvalidate();
- recycleVelocity();
- break;
- }
-
- return true;
- }
-
-
-
-
-
-
- private boolean shouldScrollToNext()
- {
- return mScrollEnd - mScrollStart > mScreenHeight / 2 || Math.abs(getVelocity()) > 600;
- }
-
-
-
-
-
-
- private boolean wantScrollToNext()
- {
- return mScrollEnd > mScrollStart;
- }
-
-
-
-
-
-
- private boolean shouldScrollToPre()
- {
- return -mScrollEnd + mScrollStart > mScreenHeight / 2 || Math.abs(getVelocity()) > 600;
- }
-
-
-
-
-
-
- private boolean wantScrollToPre()
- {
- return mScrollEnd < mScrollStart;
- }
-
- @Override
- public void computeScroll()
- {
- super.computeScroll();
- if (mScroller.computeScrollOffset())
- {
- scrollTo(0, mScroller.getCurrY());
- postInvalidate();
- } else
- {
-
- int position = getScrollY() / mScreenHeight;
-
- Log.e("xxx", position + "," + currentPage);
- if (position != currentPage)
- {
- if (mOnPageChangeListener != null)
- {
- currentPage = position;
- mOnPageChangeListener.onPageChange(currentPage);
- }
- }
-
- isScrolling = false;
- }
-
- }
-
-
-
-
-
-
- private int getVelocity()
- {
- mVelocityTracker.computeCurrentVelocity(1000);
- return (int) mVelocityTracker.getYVelocity();
- }
-
-
-
-
- private void recycleVelocity()
- {
- if (mVelocityTracker != null)
- {
- mVelocityTracker.recycle();
- mVelocityTracker = null;
- }
- }
-
-
-
-
-
-
- private void obtainVelocity(MotionEvent event)
- {
- if (mVelocityTracker == null)
- {
- mVelocityTracker = VelocityTracker.obtain();
- }
- mVelocityTracker.addMovement(event);
- }
-
-
-
-
-
-
- public void setOnPageChangeListener(OnPageChangeListener onPageChangeListener)
- {
- mOnPageChangeListener = onPageChangeListener;
- }
-
-
-
-
-
-
-
- public interface OnPageChangeListener
- {
- void onPageChange(int currentPage);
- }
- }
注释还是相当详细的,我简单描述一下,Action_down时获得当前的scrollY,然后Action_move时,根据移动的距离不断scrollby就行了,当前处理了一下边界判断,在Action_up中再次获得scrollY,两个的scrollY进行对比,然后根据移动的距离与方向决定最后的动作。
3、主Activity
- package com.example.verticallinearlayout;
-
- import android.app.Activity;
- import android.os.Bundle;
- import android.widget.Toast;
-
- import com.example.verticallinearlayout.VerticalLinearLayout.OnPageChangeListener;
-
- public class MainActivity extends Activity
- {
- private VerticalLinearLayout mMianLayout;
-
- @Override
- protected void onCreate(Bundle savedInstanceState)
- {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_main);
-
- mMianLayout = (VerticalLinearLayout) findViewById(R.id.id_main_ly);
- mMianLayout.setOnPageChangeListener(new OnPageChangeListener()
- {
- @Override
- public void onPageChange(int currentPage)
- {
-
- Toast.makeText(MainActivity.this, "第"+(currentPage+1)+"页", Toast.LENGTH_SHORT).show();
- }
- });
- }
-
- }
为了提供可扩展性,还是定义了回调接口,完全可以把这个当成一个垂直的ViewPager使用。
总结下:
Scroller这个辅助类还是相当好用的,原理我简单说一下:每次滚动时,让Scroller进行滚动,然后调用postInvalidate方法,这个方法会引发调用onDraw方法,onDraw方法中会去调用computeScroll方法,然后我们在computScroll中判断,Scroller的滚动是否结束,没有的话,把当前的View滚动到现在Scroller的位置,然后继续调用postInvalidate,这样一个循环的过程。
画张图方便大家理解,ps:没找到什么好的画图工具,那rose随便画了,莫计较。
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