安卓学习记录--引导页底部跟随小圆点

第一次发博客，希望给刚学的同学提供一点点帮助，同时也是记录自己的学习成果和成长历程，开车….呸，开始吧。

效果如下：

滑动屏幕下方小圆点跟随移动

布局文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">

<android.support.v4.view.ViewPager
android:id="@+id/vp_guild"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v4.view.ViewPager>

<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_alignParentBottom="true"
android:layout_marginBottom="30dp">
<LinearLayout
android:id="@+id/ll_point"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
>
</LinearLayout>
<View
android:id="@+id/red_point"
android:layout_width="10dp"
android:layout_height="10dp"
android:background="@drawable/shape_point_red"
></View>
</RelativeLayout>

</RelativeLayout>

三个小灰点用的是线性布局，因为小红点是覆盖在小灰点上方，所以外面套一个相对布局。

先给ViewPager填充图片

ArrayList<View> ivList=new ArrayList<View>();

for(int i=0;i<imageIds.length;i++){
ImageView iv= new ImageView(this);
iv.setBackgroundResource(imageIds[i]);
ivList.add(iv);
}

在给线性布局充填充小圆点

LinearLayout llPoint=(LinearLayout) findViewById(R.id.ll_point);

for(int i=0;i<imageIds.length;i++){
View point=new View(this);    point.setBackgroundResource(R.drawable.shape_point_gray);
LinearLayout.LayoutParams params=new LinearLayout.LayoutParams(15,15);
if(i>0){
params.leftMargin=20;
}
point.setLayoutParams(params);
llPoint.addView(point);

接下来就是在ViewPager的事件监听中，计算滑动移动的距离，和给红点设置参数了

注意：计算两个点之间的距离时，要在Layout加载完了之后才能计算，不然得到的是0，因为在onCreate中计算的话，这时还没有执行测量和绘制Layout的方法(measure()和layout())，可以让灰点绘制完后计算，具体做法如下：

llPoint.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
length=llPoint.getChildAt(1).getLeft()-llPoint.getChildAt(0).getLeft();
}
});

贴上具体实现代码

import android.app.Activity;
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.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;

import java.util.ArrayList;

public class GuildActivity extends Activity {
private static final int[] imageIds=new int[]{
R.drawable.shit_1,
R.drawable.shit_2,
R.drawable.shit_3
};
private ViewPager vpGuild;
private LinearLayout llPoint;
private ArrayList<View> ivList;
private View redPoint;
private static int length;

@Override<
4000
/span>
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_guild);
initParam();
initPage();
initEvent();
}

private void initEvent() {
vpGuild.setAdapter(new GuildAdpter());
vpGuild.setOnPageChangeListener(new PageChange());
llPoint.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
length=llPoint.getChildAt(1).getLeft()-llPoint.getChildAt(0).getLeft();
}
});
}

private void initParam() {
vpGuild= (ViewPager) findViewById(R.id.vp_guild);
llPoint=  (LinearLayout) findViewById(R.id.ll_point);
redPoint=findViewById(R.id.red_point);
}

public void initPage(){
ivList=new ArrayList<View>();
for(int i=0;i<imageIds.length;i++){
ImageView iv= new ImageView(this);
iv.setBackgroundResource(imageIds[i]);
ivList.add(iv);
}
//初始化小圆点
for(int i=0;i<imageIds.length;i++){
View point=new View(this);
point.setBackgroundResource(R.drawable.shape_point_gray);
LinearLayout.LayoutParams params=new LinearLayout.LayoutParams(15,15);
if(i>0){
params.leftMargin=20;
}
point.setLayoutParams(params);
llPoint.addView(point);
}

}

class PageChange implements ViewPager.OnPageChangeListener{

@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
float distance=length*(position+positionOffset);
RelativeLayout.LayoutParams params= (RelativeLayout.LayoutParams) redPoint.getLayoutParams();
params.leftMargin=Math.round(distance);
redPoint.setLayoutParams(params);
}

@Override
public void onPageSelected(int position) {  //当前页面的页数

}

@Override
public void onPageScrollStateChanged(int state) {
//1:拖动状态 2：安放 3：空闲
}
}

class GuildAdpter extends PagerAdapter{

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

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

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

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

}