Android仿今日头条顶部导航栏效果的实例代码

package com.rainsong.toutiaotabdemo; 
import java.util.ArrayList; 
import java.util.List; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentActivity; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentPagerAdapter; 
import android.support.v4.view.ViewPager; 
public class MainActivity extends FragmentActivity { 
 private CategoryTabStrip tabs; 
 private ViewPager pager; 
 private MyPagerAdapter adapter; 
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
 super.onCreate(savedInstanceState); 
 setContentView(R.layout.activity_main); 
 tabs = (CategoryTabStrip) findViewById(R.id.category_strip); 
 pager = (ViewPager) findViewById(R.id.view_pager); 
 adapter = new MyPagerAdapter(getSupportFragmentManager()); 
 pager.setAdapter(adapter); 
 tabs.setViewPager(pager); 
 } 
 public class MyPagerAdapter extends FragmentPagerAdapter { 
 private final List catalogs = new ArrayList(); 
 public MyPagerAdapter(FragmentManager fm) { 
 super(fm); 
 catalogs.add(getString(R.string.category_hot)); 
 catalogs.add("u672cu5730"); 
 catalogs.add(getString(R.string.category_video)); 
 catalogs.add(getString(R.string.category_society)); 
 catalogs.add(getString(R.string.category_entertainment)); 
 catalogs.add(getString(R.string.category_tech)); 
 catalogs.add(getString(R.string.category_finance)); 
 catalogs.add(getString(R.string.category_military)); 
 catalogs.add(getString(R.string.category_world)); 
 catalogs.add(getString(R.string.category_image_ppmm)); 
 catalogs.add(getString(R.string.category_health)); 
 catalogs.add(getString(R.string.category_government)); 
 } 
 @Override 
 public CharSequence getPageTitle(int position) { 
 return catalogs.get(position); 
 } 
 @Override 
 public int getCount() { 
 return catalogs.size(); 
 } 
 @Override 
 public Fragment getItem(int position) { 
 return NewsFragment.newInstance(position); 
 } 
 } 
} 

package com.rainsong.toutiaotabdemo; 
import android.content.Context; 
import android.graphics.Canvas; 
import android.graphics.Rect; 
import android.graphics.drawable.Drawable; 
import android.support.v4.view.ViewPager; 
import android.support.v4.view.ViewPager.OnPageChangeListener; 
import android.util.AttributeSet; 
import android.util.DisplayMetrics; 
import android.util.TypedValue; 
import android.view.Gravity; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.HorizontalScrollView; 
import android.widget.LinearLayout; 
import android.widget.TextView; 
public class CategoryTabStrip extends HorizontalScrollView { 
 private LayoutInflater mLayoutInflater; 
 private final PageListener pageListener = new PageListener(); 
 private ViewPager pager; 
 private LinearLayout tabsContainer; 
 private int tabCount; 
 private int currentPosition = 0; 
 private float currentPositionOffset = 0f; 
 private Rect indicatorRect; 
 private LinearLayout.LayoutParams defaultTabLayoutParams; 
 private int scrollOffset = 10; 
 private int lastScrollX = 0; 
 private Drawable indicator; 
 private TextDrawable[] drawables; 
 private Drawable left_edge; 
 private Drawable right_edge; 
 public CategoryTabStrip(Context context) { 
 this(context, null); 
 } 
 public CategoryTabStrip(Context context, AttributeSet attrs) { 
 this(context, attrs, 0); 
 } 
 public CategoryTabStrip(Context context, AttributeSet attrs, int defStyle) { 
 super(context, attrs, defStyle); 
 mLayoutInflater = LayoutInflater.from(context); 
 drawables = new TextDrawable[3]; 
 int i = 0; 
 while (i < drawables.length) { 
 drawables[i] = new TextDrawable(getContext()); 
 i++; 
 } 
 indicatorRect = new Rect(); 
 setFillViewport(true); 
 setWillNotDraw(false); 
 // 标签容器 
 tabsContainer = new LinearLayout(context); 
 tabsContainer.setOrientation(LinearLayout.HORIZONTAL); 
 tabsContainer.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)); 
 addView(tabsContainer); 
 DisplayMetrics dm = getResources().getDisplayMetrics(); 
 scrollOffset = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, scrollOffset, dm); 
 defaultTabLayoutParams = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT); 
 // 绘制高亮区域作为滑动分页指示器 
 indicator = getResources().getDrawable(R.drawable.bg_category_indicator); 
 // 左右边界阴影效果 
 left_edge = getResources().getDrawable(R.drawable.ic_category_left_edge); 
 right_edge = getResources().getDrawable(R.drawable.ic_category_right_edge); 
 } 
 // 绑定与CategoryTabStrip控件对应的ViewPager控件，实现联动 
 public void setViewPager(ViewPager pager) { 
 this.pager = pager; 
 if (pager.getAdapter() == null) { 
 throw new IllegalStateException("ViewPager does not have adapter instance."); 
 } 
 pager.setOnPageChangeListener(pageListener); 
 notifyDataSetChanged(); 
 } 
 // 当附加在ViewPager适配器上的数据发生变化时,应该调用该方法通知CategoryTabStrip刷新数据 
 public void notifyDataSetChanged() { 
 tabsContainer.removeAllViews(); 
 tabCount = pager.getAdapter().getCount(); 
 for (int i = 0; i < tabCount; i++) { 
 addTab(i, pager.getAdapter().getPageTitle(i).toString()); 
 } 
 } 
 // 添加一个标签到导航菜单 
 private void addTab(final int position, String title) { 
 ViewGroup tab = (ViewGroup)mLayoutInflater.inflate(R.layout.category_tab, this, false); 
 TextView category_text = (TextView) tab.findViewById(R.id.category_text); 
 category_text.setText(title); 
 category_text.setGravity(Gravity.CENTER); 
 category_text.setSingleLine(); 
 category_text.setFocusable(true); 
 category_text.setTextColor(getResources().getColor(R.color.category_tab_text)); 
 tab.setOnClickListener(new OnClickListener() { 
 @Override 
 public void onClick(View v) { 
 pager.setCurrentItem(position); 
 } 
 }); 
 tabsContainer.addView(tab, position, defaultTabLayoutParams); 
 } 
 // 计算滑动过程中矩形高亮区域的上下左右位置 
 private void calculateIndicatorRect(Rect rect) { 
 ViewGroup currentTab = (ViewGroup)tabsContainer.getChildAt(currentPosition); 
 TextView category_text = (TextView) currentTab.findViewById(R.id.category_text); 
 float left = (float) (currentTab.getLeft() + category_text.getLeft()); 
 float width = ((float) category_text.getWidth()) + left; 
 if (currentPositionOffset > 0f && currentPosition < tabCount - 1) { 
 ViewGroup nextTab = (ViewGroup)tabsContainer.getChildAt(currentPosition + 1); 
 TextView next_category_text = (TextView) nextTab.findViewById(R.id.category_text); 
 float next_left = (float) (nextTab.getLeft() + next_category_text.getLeft()); 
 left = left * (1.0f - currentPositionOffset) + next_left * currentPositionOffset; 
 width = width * (1.0f - currentPositionOffset) + currentPositionOffset * (((float) next_category_text.getWidth()) + next_left); 
 } 
 rect.set(((int) left) + getPaddingLeft(), getPaddingTop() + currentTab.getTop() + category_text.getTop(), 
 ((int) width) + getPaddingLeft(), currentTab.getTop() + getPaddingTop() + category_text.getTop() + category_text.getHeight()); 
 } 
 // 计算滚动范围 
 private int getScrollRange() { 
 return getChildCount() > 0 ? Math.max(0, getChildAt(0).getWidth() - getWidth() + getPaddingLeft() + getPaddingRight()) : 0; 
 } 
 // CategoryTabStrip与ViewPager联动逻辑 
 private void scrollToChild(int position, int offset) { 
 if (tabCount == 0) { 
 return; 
 } 
 calculateIndicatorRect(indicatorRect); 
 int newScrollX = lastScrollX; 
 if (indicatorRect.left < getScrollX() + scrollOffset) { 
 newScrollX = indicatorRect.left - scrollOffset; 
 } else if (indicatorRect.right > getScrollX() + getWidth() - scrollOffset) { 
 newScrollX = indicatorRect.right - getWidth() + scrollOffset; 
 } 
 if (newScrollX != lastScrollX) { 
 lastScrollX = newScrollX; 
 scrollTo(newScrollX, 0); 
 } 
 } 
 // 自定义绘图 
 @Override 
 public void draw(Canvas canvas) { 
 super.draw(canvas); 
 // 绘制高亮背景矩形红框 
 calculateIndicatorRect(indicatorRect); 
 if(indicator != null) { 
 indicator.setBounds(indicatorRect); 
 indicator.draw(canvas); 
 } 
 // 绘制背景红框内标签文本 
 int i = 0; 
 while (i < tabsContainer.getChildCount()) { 
 if (i < currentPosition - 1 || i > currentPosition + 1) { 
 i++; 
 } else { 
 ViewGroup tab = (ViewGroup)tabsContainer.getChildAt(i); 
 TextView category_text = (TextView) tab.findViewById(R.id.category_text); 
 if (category_text != null) { 
 TextDrawable textDrawable = drawables[i - currentPosition + 1]; 
 int save = canvas.save(); 
 calculateIndicatorRect(indicatorRect); 
 canvas.clipRect(indicatorRect); 
 textDrawable.setText(category_text.getText()); 
 textDrawable.setTextSize(0, category_text.getTextSize()); 
 textDrawable.setTextColor(getResources().getColor(R.color.category_tab_highlight_text)); 
 int left = tab.getLeft() + category_text.getLeft() + (category_text.getWidth() - textDrawable.getIntrinsicWidth()) / 2 + getPaddingLeft(); 
 int top = tab.getTop() + category_text.getTop() + (category_text.getHeight() - textDrawable.getIntrinsicHeight()) / 2 + getPaddingTop(); 
 textDrawable.setBounds(left, top, textDrawable.getIntrinsicWidth() + left, textDrawable.getIntrinsicHeight() + top); 
 textDrawable.draw(canvas); 
 canvas.restoreToCount(save); 
 } 
 i++; 
 } 
 } 
 // 绘制左右边界阴影效果 
 i = canvas.save(); 
 int top = getScrollX(); 
 int height = getHeight(); 
 int width = getWidth(); 
 canvas.translate((float) top, 0.0f); 
 if (left_edge == null || top <= 0) { 
 if (right_edge == null || top >= getScrollRange()) { 
 canvas.restoreToCount(i); 
 } 
 right_edge.setBounds(width - right_edge.getIntrinsicWidth(), 0, width, height); 
 right_edge.draw(canvas); 
 canvas.restoreToCount(i); 
 } 
 left_edge.setBounds(0, 0, left_edge.getIntrinsicWidth(), height); 
 left_edge.draw(canvas); 
 if (right_edge == null || top >= getScrollRange()) { 
 canvas.restoreToCount(i); 
 } 
 right_edge.setBounds(width - right_edge.getIntrinsicWidth(), 0, width, height); 
 right_edge.draw(canvas); 
 canvas.restoreToCount(i); 
 } 
 private class PageListener implements OnPageChangeListener { 
 @Override 
 public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { 
 currentPosition = position; 
 currentPositionOffset = positionOffset; 
 scrollToChild(position, (int) (positionOffset * tabsContainer.getChildAt(position).getWidth())); 
 invalidate(); 
 } 
 @Override 
 public void onPageScrollStateChanged(int state) { 
 if (state == ViewPager.SCROLL_STATE_IDLE) { 
 if(pager.getCurrentItem() == 0) { 
 // 滑动到最左边 
 scrollTo(0, 0); 
 } else if (pager.getCurrentItem() == tabCount - 1) { 
 // 滑动到最右边 
 scrollTo(getScrollRange(), 0); 
 } else { 
 scrollToChild(pager.getCurrentItem(), 0); 
 } 
 } 
 } 
 @Override 
 public void onPageSelected(int position) { 
 } 
 } 
}