Android仿微信底部按钮滑动变色

 //这个监听有三个方法 public abstract void onPageScrollStateChanged (int state) public abstract void onPageScrolled (int position, float positionOffset, int positionOffsetPixels) public abstract void onPageSelected (int position) //第一个方法onPageScrollStateChanged 中的参数state，有三个可取的值 public static final int SCROLL_STATE_DRAGGING Constant Value: 1 (0x00000001) //手指按在ViewPager上滑动时 public static final int SCROLL_STATE_IDLE Constant Value: 0 (0x00000000) //手指松开后，ViewPager自动滑动期间 public static final int SCROLL_STATE_SETTLING Constant Value: 2 (0x00000002) //ViewPager进入了某个Page //如果在onPageScrollStateChanged 中输出state的值，你会发现每次都是按顺序打印出“1---2---0” //第二个方法onPageScrolled的三个参数 position：//滑动时，屏幕左侧显示的第一个page positionOffset：//滑动比例，值的范围为[0, 1)，手指往左滑动，该值递增，反之递减 positionOffsetPixels：//滑动距离，和屏幕有关，手指往左滑动，该值递增，反之递减 //我们经常需要检查viewpager的滑动方向并作出一些操作，这时你只需要通过position和positionOffset两个值即可实现该功能。 //比如实现微信底部图标颜色渐变 向左滑动时 ChangeColorIconWithTextView left = mTabIndicator.get(position); //左侧显示的第一个page页面上底部图标和文字的初始化 ChangeColorIconWithTextView right = mTabIndicator.get(position + 1); //右侧显示的Page底部图标和文字的初始化 left.setIconAlpha(1 - positionOffset); //设置图标的透明度 此时positionOffset值递增 左侧图标的颜色变浅 right.setIconAlpha(positionOffset); //右侧图标的颜色逐渐变深 //第三个方法onPageSelected的三个参数 position：//当前选择的page序号 //该方法被调用的时间比较特别，在上面的第一个方法中的“1---2----0”中的2执行之后，onPageSelected就执行，然后执行“1---2----0”中的0。就是手指松开屏幕之后，onPageSelected被执行。 

 package com.mhealth.nursestation.app.pda.business.login.base.ui.fragmentutil; import android.content.Context; import android.content.res.TypedArray; import android.graphics.Bitmap; import android.graphics.Bitmap.Config; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Paint; import android.graphics.PorterDuff; import android.graphics.PorterDuffXfermode; import android.graphics.Rect; import android.graphics.drawable.BitmapDrawable; import android.os.Bundle; import android.os.Looper; import android.os.Parcelable; import android.util.AttributeSet; import android.util.TypedValue; import android.view.View; import com.mhealth.nursestation.app.pda.R; /** * 此类用于修改颜色渐变 */ public class ChangeColorIconWithTextView extends View { private Bitmap mBitmap; private Canvas mCanvas; private Paint mPaint; /** * 颜色 */ private int mColor = 0XFF07B7C4; /** * 透明度 0.0-1.0 初始化必须是0 不是0就废了 */ private float mAlpha = 0f; /** * 图标 */ private Bitmap mIconBitmap; /** * 限制绘制icon的范围 */ private Rect mIconRect; /** * icon底部文本 */ private String mText = "微信"; private int mTextSize = (int) TypedValue.applyDimension( TypedValue.COMPLEX_UNIT_SP, 10, getResources().getDisplayMetrics()); private Paint mTextPaint; private Rect mTextBound = new Rect(); public ChangeColorIconWithTextView(Context context) { super(context); } /** * 初始化自定义属性值 * * @param context * @param attrs */ public ChangeColorIconWithTextView(Context context, AttributeSet attrs) { super(context, attrs); // 获取设置的图标 TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ChangeColorIconView); int n = a.getIndexCount(); for (int i = 0; i 

 @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { if (positionOffset > 0) { ChangeColorIconWithTextView left = mTabIndicator.get(position); ChangeColorIconWithTextView right = mTabIndicator.get(position + 1); left.setIconAlpha(1 - positionOffset); right.setIconAlpha(positionOffset); } } 

 private List mTabIndicator = new ArrayList(); private void initTabIndicator() { ChangeColorIconWithTextView one = (ChangeColorIconWithTextView) findViewById(R.id.id_indicator_one); ChangeColorIconWithTextView two = (ChangeColorIconWithTextView) findViewById(R.id.id_indicator_two); ChangeColorIconWithTextView three = (ChangeColorIconWithTextView) findViewById(R.id.id_indicator_three); ChangeColorIconWithTextView four = (ChangeColorIconWithTextView) findViewById(R.id.id_indicator_four); mTabIndicator.add(one); mTabIndicator.add(two); mTabIndicator.add(three); mTabIndicator.add(four); one.setOnClickListener(this); two.setOnClickListener(this); three.setOnClickListener(this); four.setOnClickListener(this); one.setIconAlpha(1.0f); } 

 @Override public void onClick(View v) { resetOtherTabs(); switch (v.getId()) { case R.id.id_indicator_one: mTabIndicator.get(0).setIconAlpha(1.0f); mViewPager.setCurrentItem(0, false); break; case R.id.id_indicator_two: mTabIndicator.get(1).setIconAlpha(1.0f); mViewPager.setCurrentItem(1, false); break; case R.id.id_indicator_three: mTabIndicator.get(2).setIconAlpha(1.0f); mViewPager.setCurrentItem(2, false); mAppContext.has_new_talk = false; break; case R.id.id_indicator_four: mTabIndicator.get(3).setIconAlpha(1.0f); mViewPager.setCurrentItem(3, false); break; } }