Android自定义控件（一）
一 、自定义控件的一些概念
1、什么是自定义控件
在Android系统中，用系统的自带控件重新组合或者自定义类继承View或者自定义类继承ViewGroup，实现特定的UI效 果。
2、为什么要学习自定义控件
（1）系统的某些控件在不同设备显示效果不一样（android系统版本影响，或者各手机场上的UI优化）。
（2）整个软件在不同设备风格统一
（3）系统自带的控件功能有限，增加功能或功能太多，减少功能 。
3、自定义控件的重要性
（1）View和ViewGrop的区别
（2）Android的时间传递
（3）View的原理
二、 自定义控件的分类
1、 系统控件重新组合
2、自定义类继承View
3、自定义类继承VeiwGroup
三、 自定义控件实例
系统控件重新组合（ViewPager的使用）
主要功能实现ViewPager自动无限轮播，并加入当前页标记原点。效果图如下
package com.zcwang.viewpager; import android.content.Context; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.support.v4.view.PagerAdapter; import android.support.v4.view.ViewPager; import android.support.v7.app.AppCompatActivity; import android.view.MotionEvent; import android.view.View; import android.view.ViewGroup; import android.widget.ImageView; import android.widget.LinearLayout; import java.util.ArrayList; import java.util.List; public class MainActivity extends AppCompatActivity { private ViewPager mViewPager; private LinearLayout mPointContainer; private int mPrePosition; private int [] images = new int[]{R.drawable.a1,R.drawable.a2,R.drawable.a3, R.drawable.a4, R.drawable.a5,R.drawable.a6,R.drawable.a7, R.drawable.a8,R.drawable.a9}; private List<ImageView> imageViewList; private Handler mHandler = new Handler(){ @Override public void handleMessage(Message msg) { super.handleMessage(msg); int item = mViewPager.getCurrentItem()+1; mViewPager.setCurrentItem(item); mHandler.sendEmptyMessageDelayed(0,4000); } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mViewPager = (ViewPager) findViewById(R.id.view_pager); mPointContainer = (LinearLayout) findViewById(R.id.vp_point_container); imageViewList = new ArrayList<>(); for (int i= 0;i<images.length;i++){ ImageView image=new ImageView(this); image.setBackgroundResource(images[i]); imageViewList.add(image); ImageView point = new ImageView(this); point.setBackgroundResource(R.drawable.point_selector); LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(dip2px(this,8),dip2px(this,8)); params.leftMargin = dip2px(this,8); if (i==0){ point.setEnabled(true); }else { point.setEnabled(false); point.setLayoutParams(params); } mPointContainer.addView(point); } mViewPager.setAdapter(new MyViewPagerAdapter()); mViewPager.setCurrentItem(Integer.MAX_VALUE/2); mViewPager.setOnPageChangeListener(new MyViewPagerChangeListener()); mHandler.sendEmptyMessageDelayed(0,4000); } private class MyViewPagerAdapter extends PagerAdapter { @Override public int getCount() { return Integer.MAX_VALUE; } @Override public Object instantiateItem(ViewGroup container, int position) { int realPosition = position%images.length; ImageView image = imageViewList.get(realPosition); image.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: mHandler.removeCallbacksAndMessages(null); break; case MotionEvent.ACTION_UP: mHandler.removeCallbacksAndMessages(null); mHandler.sendEmptyMessageDelayed(0,4000); break; } return true; } }); container.addView(image); return image; } @Override public void destroyItem(ViewGroup container, int position, Object object) { container.removeView((View) object); } @Override public boolean isViewFromObject(View view, Object object) { return view==object; } } public static int dip2px(Context context, float dpValue) { float scale = context.getResources().getDisplayMetrics().density; return (int) (dpValue * scale + 0.5f); } private class MyViewPagerChangeListener implements ViewPager.OnPageChangeListener { @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { } @Override public void onPageSelected(int position) { int realPosition = position%images.length; mPointContainer.getChildAt(mPrePosition).setEnabled(false); mPointContainer.getChildAt(realPosition).setEnabled(true); mPrePosition = realPosition; } @Override public void onPageScrollStateChanged(int state) { if (state == ViewPager.SCROLL_STATE_DRAGGING){ mHandler.removeCallbacksAndMessages(null); }else if (state ==ViewPager.SCROLL_STATE_IDLE){ mHandler.removeCallbacksAndMessages(null); mHandler.sendEmptyMessageDelayed(0,4000); } } } @Override protected void onDestroy() { super.onDestroy(); mHandler.removeCallbacksAndMessages(null); } }
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="oval"> <size android:height="8dp" android:width="8dp"/> <solid android:color="#44000000"/> </shape>
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="oval"> <size android:height="8dp" android:width="8dp"/> <solid android:color="#ff0000"/> </shape>
<?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:state_enabled="false" android:drawable="@drawable/point_normal"/> <item android:state_enabled="true" android:drawable="@drawable/point_select"/> </selector>
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.zcwang.viewpager.MainActivity"> <RelativeLayout android:layout_width="match_parent" android:layout_height="200dp"> <android.support.v4.view.ViewPager android:id="@+id/view_pager" android:layout_width="match_parent" android:layout_height="match_parent"/> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical" android:layout_alignParentBottom="true"> <TextView android:id="@+id/vp_text" android:layout_gravity="center_horizontal" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="454646545646465464"/> <LinearLayout android:orientation="horizontal" android:id="@+id/vp_point_container" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" /> </LinearLayout> </RelativeLayout> </RelativeLayout>