Android Tab 选项卡 切换

package com.jcdh.jcli.activitytabswitch; //ViewPager + Fragment + FragmentPagerAdapter import android.app.Activity; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentActivity; import android.support.v4.view.ViewPager; import android.util.DisplayMetrics; import android.util.Log; import android.view.View; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.TextView; import java.util.ArrayList; public class MainActivity extends FragmentActivity implements View.OnClickListener, ViewPager.OnPageChangeListener { // 三个textview private TextView tab1Tv, tab2Tv, tab3Tv; // 指示器 private ImageView cursorImg; // viewpager private ViewPager viewPager; // fragment对象集合 private ArrayList<Fragment> fragmentsList; // 记录当前选中的tab的index private int currentIndex = 0; // 指示器的偏移量 private int offset = 0; // 左margin private int leftMargin = 0; // 屏幕宽度 private int screenWidth = 0; // 屏幕宽度的三分之一 private int screen1_3; // private LinearLayout.LayoutParams lp; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); init(); } /** * 初始化操作 */ private void init() { DisplayMetrics dm = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(dm); screenWidth = dm.widthPixels; screen1_3 = screenWidth / 3; cursorImg = (ImageView) findViewById(R.id.cursor); lp = (LinearLayout.LayoutParams) cursorImg.getLayoutParams(); leftMargin = lp.leftMargin; tab1Tv = (TextView) findViewById(R.id.tab1_tv); tab2Tv = (TextView) findViewById(R.id.tab2_tv); tab3Tv = (TextView) findViewById(R.id.tab3_tv); // tab1Tv.setOnClickListener(this); tab2Tv.setOnClickListener(this); tab3Tv.setOnClickListener(this); initViewPager(); } /** * 初始化viewpager */ private void initViewPager() { viewPager = (ViewPager) findViewById(R.id.third_vp); fragmentsList = new ArrayList<Fragment>(); Fragment fragment = new Tab1Fragment(); fragmentsList.add(fragment); fragment = new Tab2Fragment(); fragmentsList.add(fragment); fragment = new Tab3Fragment(); fragmentsList.add(fragment); viewPager.setAdapter(new FragmentAdapter(getSupportFragmentManager(), fragmentsList)); viewPager.setCurrentItem(0); viewPager.setOnPageChangeListener(this); } @Override public void onClick(View v) { switch (v.getId()) { case R.id.tab1_tv: viewPager.setCurrentItem(0); break; case R.id.tab2_tv: viewPager.setCurrentItem(1); break; case R.id.tab3_tv: viewPager.setCurrentItem(2); break; } } @Override public void onPageScrollStateChanged(int arg0) { } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { offset = (screen1_3 - cursorImg.getLayoutParams().width) / 2; Log.d("111", position + "--" + positionOffset + "--" + positionOffsetPixels); final float scale = getResources().getDisplayMetrics().density; if (position == 0) {// 0<->1 lp.leftMargin = (int) (positionOffsetPixels / 3) + offset; } else if (position == 1) {// 1<->2 lp.leftMargin = (int) (positionOffsetPixels / 3) + screen1_3 +offset; } cursorImg.setLayoutParams(lp); currentIndex = position; } @Override public void onPageSelected(int arg0) { } }