引導小圓點

閒來無事，整理一下以前寫的小Demo，分享給大家。

本次分享的是APP引導頁當中的小圓點的實現方式。

先看效果圖

佈局：

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.android.guide.MainActivity">

    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="20dp" >

        <LinearLayout
            android:id="@+id/dot_group"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal" >
        </LinearLayout>

        <View
            android:id="@+id/view_red_point"
            android:layout_width="10dp"
            android:layout_height="10dp"
            android:background="@drawable/guide_dot_color" />
    </RelativeLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/guide_vp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"/>

    <Button
        android:id="@+id/start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="開始"
        android:visibility="gone"/>
</RelativeLayout>

兩個圓點都是使用shape畫出來的
黑點

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
<corners android:radius="5dp"/>
    <solid android:color="#000"/>
</shape>

紅點

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
    <corners android:radius="5dp"/>
    <solid android:color="#f00"/>

</shape>

下面上重要部分，代碼中都有解釋，不多做介紹哦！

package com.android.guide;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends Activity {

    private ViewPager mViewPager;
    private Button mStart;
    private List<ImageView> mImageViewList; //引導頁的ImageView集合
    private LinearLayout mPointGroup; //點的集合
    private View mDot; //紅點
    private int mDotWidth; //點的間距

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mViewPager = (ViewPager) findViewById(R.id.guide_vp);
        mStart = (Button) findViewById(R.id.start);
        mPointGroup = (LinearLayout) findViewById(R.id.dot_group);
        mDot = findViewById(R.id.view_red_point);
        initData();
        mViewPager.setAdapter(new GuideAdapter());
        mViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

            /**
             * 頁面滑動監聽
             *
             * @params position 當前選中的位置
             * @params positionOffset 偏移百分比
             * @params positionOffsetPixels 頁面偏移長度
             */
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                int leftMargin = (int) (mDotWidth * (positionOffset + position));
                RelativeLayout.LayoutParams lp = (android.widget.RelativeLayout.LayoutParams) mDot
                        .getLayoutParams();
                lp.leftMargin = leftMargin;
                mDot.setLayoutParams(lp);
            }

            @Override
            public void onPageSelected(int position) {
                if (position == mImageViewList.size() - 1){
                    mStart.setVisibility(View.VISIBLE);
                }else {
                    mStart.setVisibility(View.GONE);
                }
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });

        // 獲得視圖樹觀察者, 觀察當整個佈局的layout時的事件
        mDot.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {

            // 完成佈局後會回調改方法, 改方法可能會被回調多次
            @Override
            public void onGlobalLayout() {
                // 此方法只需要執行一次就可以: 把當前的監聽事件從視圖樹中移除掉, 以後就不會在回調此事件了.
                mDot.getViewTreeObserver().removeGlobalOnLayoutListener(this);
                mDotWidth = mPointGroup.getChildAt(1).getLeft() - mPointGroup.getChildAt(0).getLeft();
            }
        });

        mStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(MainActivity.this,OtherActivity.class));
            }
        });
    }

    private void initData() {
        int[] imageResID = {R.drawable.ic_launcher,
                R.drawable.ic_launcher,
                R.drawable.ic_launcher,
                R.drawable.ic_launcher};

        mImageViewList = new ArrayList<ImageView>();

        for (int i = 0; i < imageResID.length; i++) {
            ImageView image = new ImageView(this);
            image.setBackgroundResource(imageResID[i]);
            mImageViewList.add(image);

            View dot = new View(this);
            dot.setBackgroundResource(R.drawable.guide_point_default);

            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                    dp2px(this, 10), dp2px(this, 10));

            if (i != 0) {
                params.leftMargin = dp2px(this, 10);
            }

            dot.setLayoutParams(params);
            mPointGroup.addView(dot);
        }
    }

    /**
     * dp轉px
     *
     * @param context
     * @param dp
     * @return
     */
    private int dp2px(Context context, float dp) {
        float density = context.getResources().getDisplayMetrics().density;
        int px = (int) (dp * density + 0.5f);
        return px;
    }

    class GuideAdapter extends PagerAdapter {

        @Override
        public int getCount() {
            return mImageViewList.size();
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == object;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((ImageView) object);
        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            container.addView(mImageViewList.get(position));
            return mImageViewList.get(position);
        }
    }
}

怎麼樣，是不是很簡單。

源碼下載(^__^) 嘻嘻……