Android自定义TabLayout效果

周末就要到了，今天项目中遇到这样一个Tab，选中tab的背景是个圆角矩形，方向指向器没有了，这样普通的TabLayout不能满足我的要求，可能会想到动态的去设置选中Tab的背景不就可以了，但是那样的话太生硬了，没有动画效果，其实想想也还比较简单，今天就简单的说一说这个YzzTab。效果如下图：

这里是四个Tab，一版只显示3个，这里假设有num个Tab，当滑动到第3个时，这里就需要考虑如何让TabLayout和指示器一起移动呢？

@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
 if (positionOffset>1){
  return;
 }
 int leftCop = (int) (positionOffset*(getMeasuredWidth()/mMaxLineNum)+position*getMeasuredWidth()/mMaxLineNum);
 if (leftCop!=leftForTabLayout){
  //这里要做判断是否滑动,当选择的位置大于TabLayout中显示的最大数-1时，会向左右滑动，指示器也会
  //跟这滑动，相对静止，否则指示器滑动，Tab布局不移动
  if (position>=mMaxLineNum-1) {
   scrollContent += leftCop - leftForTabLayout;
   scrollTo(scrollContent, 0);
   //这里要重新layout
   update();
  }
  leftForTabLayout = leftCop;
  invalidate();
 }
}

首先，在ViewPage的监听中，positionOffset有时候可能大于1，这点需要注意的，当两次left的坐标相等 时，我们就不进行绘制了，接下来就是
如何确定left的值了，对于这点我也想了很久，最后终于得出结论：

int leftCop = (int) (positionOffset*(getMeasuredWidth()/mMaxLineNum)+position*getMeasuredWidth()/mMaxLineNum);

因为当positionOffset的值在向右滑动80%左右的时候getCurrentItem（）的值会发生变化，这点可以试验一下，所以getCurrentItem（）方法不能用了，只能用参数position.Layout滑动的实际代码注释很详细了，我就不再阐述了，可以试试。在布局滑动了以后，必须要layout，不然View的属性不会变，点击没法应，但是也可以不更新，动态的告诉用户点击的真是Tab，这样也可以。

 private void update() {
 for (int i = 0; i <mChildCount ; i++) {
  View v = getChildAt(i);
  v.setLeft(v.getLeft()+scrollContent);
 }
 //必须调用，不然不会重新layout
 requestLayout();
}

接下来就是绘制了，ViewGroup是默认不调用onDraw（canvas canvas）方法的，原因很简单，ViewGroup是个容器，主要作用是起承载作用，绘画就交给子View了，但是还是有办法让其调用该方法的，如下：

 setWillNotDraw(false);

这就告诉该容器，需要绘制；

接下来就是绘制指向器和选中背景了，一个圆角矩形和一条线，比较简单，我就不再详细说明了。

@Override
protected void onDraw(Canvas canvas) {
 //left = getMeasuredWidth() / mChildCount * mSelectPosition;
 super.onDraw(canvas);
 mPaint.setColor(Color.GREEN);
 int top = getMeasuredHeight() / 4;
 int right = leftForTabLayout + getMeasuredWidth() / mMaxLineNum;
 int bottom = getMeasuredHeight() - getMeasuredHeight() / 4;
 RectF rectF = new RectF(leftForTabLayout, top, right, bottom);
 mPaint.setAntiAlias(true);
 mPaint.setStyle(Paint.Style.FILL);
 canvas.drawRoundRect(rectF, 10, 10, mPaint);
 mPaint.setColor(Color.RED);
 mPaint.setStrokeWidth(5);
 canvas.drawLine(leftForTabLayout,getMeasuredHeight()-5,right,getMeasuredHeight()-5,mPaint);
}

接下来介绍建与ViewPager建立关联的方法

 
public void setUpWithViewPager(ViewPager viewPager) {
 mViewPager = viewPager;
 mChildCount = viewPager.getAdapter().getCount();
 mSelectPosition = viewPager.getCurrentItem();
 viewPager.setOnPageChangeListener(this);
}

初始化的方法

private void init() {
 setWillNotDraw(false);
 mPaint = new Paint();
 for (int i = 0; i < mChildCount; i++) {
  final TextView tv = new TextView(getContext());
  int w = getMeasuredWidth()/mMaxLineNum;
  LinearLayout.LayoutParams lp = new LayoutParams(w, ViewGroup.LayoutParams.MATCH_PARENT);
  tv.setText("tab" + i);
  tv.setGravity(Gravity.CENTER);
  tv.setLayoutParams(lp);
  final int finalI = i;
  tv.setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
    if (monTabSelecterListener != null){
     monTabSelecterListener.selecter(finalI,tv);
    }
   }
  });
  addView(tv);
 }
}

这里只是很简单的加了几个TextView进去，也可以弄个方法，通过用户动态添加自己想要的View，都可以实现的。至于监听的话就很简单了.上面已经写到了。

YzzTab的代码

package a6he.Android.yzz.com.mytablayout;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.util.Log;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.Switch;
import android.widget.TextView;

public class YzzTab extends LinearLayout implements ViewPager.OnPageChangeListener {
private ViewPager mViewPager;
private Paint mPaint;
//tab的数量
private int mChildCount;
//tab选中的位置
private int mSelectPosition;
//绘制指向器的左顶点
private int leftForTabLayout = 0;
private int leftForInvidator = 0;
private int mMaxLineNum = 3;
private int scrollContent = 0;
private onTabSelecterListener monTabSelecterListener;
public YzzTab(Context context) {
 super(context);
}
public YzzTab(Context context, AttributeSet attrs) {
 super(context, attrs);
}
public YzzTab(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
}
@Override
protected void onFinishInflate() {
 super.onFinishInflate();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 init();
}

public void setUpWithViewPager(ViewPager viewPager) {
 mViewPager = viewPager;
 mChildCount = viewPager.getAdapter().getCount();
 mSelectPosition = viewPager.getCurrentItem();
 viewPager.setOnPageChangeListener(this);
}

private void init() {
 setWillNotDraw(false);
 mPaint = new Paint();
 for (int i = 0; i < mChildCount; i++) {
  final TextView tv = new TextView(getContext());
  int w = getMeasuredWidth()/mMaxLineNum;
  LinearLayout.LayoutParams lp = new LayoutParams(w, ViewGroup.LayoutParams.MATCH_PARENT);
  tv.setText("tab" + i);
  tv.setGravity(Gravity.CENTER);
  tv.setLayoutParams(lp);
  final int finalI = i;
  tv.setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
    if (monTabSelecterListener != null){
     monTabSelecterListener.selecter(finalI,tv);
    }
   }
  });
  addView(tv);
 }
}
@Override
protected void onDraw(Canvas canvas) {
 //left = getMeasuredWidth() / mChildCount * mSelectPosition;
 super.onDraw(canvas);
 mPaint.setColor(Color.GREEN);
 int top = getMeasuredHeight() / 4;
 int right = leftForTabLayout + getMeasuredWidth() / mMaxLineNum;
 int bottom = getMeasuredHeight() - getMeasuredHeight() / 4;
 RectF rectF = new RectF(leftForTabLayout, top, right, bottom);
 mPaint.setAntiAlias(true);
 mPaint.setStyle(Paint.Style.FILL);
 canvas.drawRoundRect(rectF, 10, 10, mPaint);
 mPaint.setColor(Color.RED);
 mPaint.setStrokeWidth(5);
 canvas.drawLine(leftForTabLayout,getMeasuredHeight()-5,right,getMeasuredHeight()-5,mPaint);
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
 if (positionOffset>1){
  return;
 }
 int leftCop = (int) (positionOffset*(getMeasuredWidth()/mMaxLineNum)+position*getMeasuredWidth()/mMaxLineNum);
 if (leftCop!=leftForTabLayout){
  //这里要做判断是否滑动,当选择的位置大于TabLayout中显示的最大数-1时，会向左右滑动，指示器也会
  //跟这滑动，相对静止，否则指示器滑动，Tab布局不移动
  if (position>=mMaxLineNum-1) {
   scrollContent += leftCop - leftForTabLayout;
   scrollTo(scrollContent, 0);
   //这里要重新layout
   update();
  }
  leftForTabLayout = leftCop;
  invalidate();
 }
}
private void update() {
 for (int i = 0; i <mChildCount ; i++) {
  View v = getChildAt(i);
  v.setLeft(v.getLeft()+scrollContent);
 }
 requestLayout();
}
@Override
public void onPageSelected(int position) {
}
@Override
public void onPageScrollStateChanged(int state) {
 switch (state){
 }
}
public void setmMaxLineNum(int mMaxLineNum) {
 this.mMaxLineNum = mMaxLineNum;
}
public void setonTabSelecterListener(onTabSelecterListener monTabSelecterListener) {
 this.monTabSelecterListener = monTabSelecterListener;
}
interface onTabSelecterListener{
 void selecter(int position,View view);
 }
}

好啦，就介绍这么多，还有待完善，继续封装，完成更强大的功能。

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