02ViewPager高度自适应轮播图
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（1）高度自适应ViewPager
（2）解决ViewPager设置高度为wrap_content无效的方法
【02】ViewPager高度自适应轮播图
文章目录
1.效果
2.源码
2.1自定义ViewPager
（1）核心子View测量
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.viewpager.widget.ViewPager;
/**
* @author XiongJie
* @version appVer
* @Package com.gdc.knowledge.highui.hightviewpager
* @file
* @Description:
* 1.高度自适应ViewPager
* （1）解决ViewPager设置高度为wrap_content无效的方法
*
* @date 2021-6-7 23:35
* @since appVer
*/
public class MyViewPager extends ViewPager
private static final String TAG = "MyViewPager";
public MyViewPager(@NonNull Context context)
super(context);
public MyViewPager(@NonNull Context context, @Nullable AttributeSet attrs)
super(context, attrs);
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
int height = 0;
Log.d(TAG, "onMeasure: getChildCount: " + getChildCount());
/**
* 1.测量子View的大小
* （1）需要将子View的大小转换为具体的宽高
*/
for(int i = 0 ; i < getChildCount(); i++)
View child = getChildAt(i);
//1.1先要获取子View的LayoutParams然后再测量
ViewGroup.LayoutParams lp = child.getLayoutParams();
int childWidthSpec = getChildMeasureSpec(widthMeasureSpec,0,lp.width);
int childHightSpec = getChildMeasureSpec(heightMeasureSpec,0,lp.height);
//1.2测量子View的大小
child.measure(childWidthSpec,childHightSpec);
//1.2获取测量之后的实际高度
int h = child.getMeasuredHeight();
if(h > height)
height = h;
Log.d(TAG, "onMeasure: " + h + " height: " + height);
//2.设置高度测量模式
heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(height,
MeasureSpec.EXACTLY);
//3.保存测量结果
setMeasuredDimension(widthMeasureSpec,heightMeasureSpec);
//4.测量ViewPager自己
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
2.1Activity
public class ViewPagerHeightWrapActivity extends AppCompatActivity
private ViewPager viewPager;
private RadioGroup radioGroup;
private List<Integer> images;
private int index;
private int preIndex;
private Timer timer = new Timer();
private boolean isContinue = true;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_pager_height_wrap);
viewPager = findViewById(R.id.view_Pager);
radioGroup = findViewById(R.id.radio_group);
images = new ArrayList<>();
images.add(R.drawable.p1);
images.add(R.drawable.p2);
images.add(R.drawable.p3);
images.add(R.drawable.p4);
images.add(R.drawable.p5);
MyPagerAdapter pagerAdapter = new MyPagerAdapter(images,this);
viewPager.setPageMargin(30);
viewPager.setOffscreenPageLimit(3);
viewPager.setAdapter(pagerAdapter);
viewPager.addOnPageChangeListener(onPageChangeListener);
viewPager.setPageTransformer(true, new PageTransform());
//指示器
initRadioButton(images.size());
//轮播
timer.schedule(new TimerTask()
@Override
public void run()
if (isContinue)
handler.sendEmptyMessage(1);
, 2000, 2000);
/**
* RadioButton
* @param length
*/
private void initRadioButton(int length)
for (int i = 0; i < length; i++)
ImageView imageView = new ImageView(this);
imageView.setImageResource(R.drawable.rg_selector);
imageView.setPadding(20, 0, 0, 0);
radioGroup.addView(imageView, ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT);
radioGroup.getChildAt(0).setEnabled(false);
ViewPager.OnPageChangeListener onPageChangeListener = new ViewPager.OnPageChangeListener()
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
@Override
public void onPageSelected(int position)
index = position;
setCurrentDot(index % images.size());
@Override
public void onPageScrollStateChanged(int state)
;
private void setCurrentDot(int i)
if (radioGroup.getChildAt(i) != null)
//当前按钮不可改变
radioGroup.getChildAt(i).setEnabled(false);
if (radioGroup.getChildAt(preIndex) != null)
//上个按钮可以改变
radioGroup.getChildAt(preIndex).setEnabled(true);
//当前位置变为上一个，继续下次轮播
preIndex = i;
Handler handler = new Handler()
@Override
public void handleMessage(Message msg)
super.handleMessage(msg);
switch (msg.what)
case 1:
index++;
viewPager.setCurrentItem(index);
;
2.3PagerAdapter
public class MyPagerAdapter extends PagerAdapter
private static final String TAG = "MyPagerAdapter";
private List<Integer> mImages;
private Context mContext;
MyPagerAdapter(List<Integer> images, Context context)
mImages = images;
mContext = context;
@Override
public int getCount()
return Integer.MAX_VALUE;
@Override
public boolean isViewFromObject(@NonNull View view, @NonNull Object object)
return view == object;
@NonNull
@Override
public Object instantiateItem(@NonNull ViewGroup container, int position)
position = position % mImages.size();
View view = LayoutInflater
.from(mContext).inflate(R.layout.linear_item, container, false);
ImageView imageView = view.findViewById(R.id.iv_page);
imageView.setImageResource(mImages.get(position));
TextView textView = view.findViewById(R.id.tv);
textView.setText(position + " ");
container.addView(view);
return view;
@Override
public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object)
container.removeView((View) object);
2.4切换特效
public class PageTransform implements ViewPager.PageTransformer
private static final float DEFAULT_MIN_ALPHA = 0.3f;
private float mMinAlpha = DEFAULT_MIN_ALPHA;
private static final float DEFAULT_MAX_ROTATE = 15.0f;
private float mMaxRotate = DEFAULT_MAX_ROTATE;
@Override
public void transformPage(@NonNull View page, float position)
if (position < -1)
//透明度
page.setAlpha(mMinAlpha);
//旋转
page.setRotation(mMaxRotate * -1);
page.setPivotX(page.getWidth());
page.setPivotY(page.getHeight());
else if(position <= 1)
if(position < 0)
/**
* （1）position是0到-1的变化,p1+position就是从1到0的变化
* （2）(p1 - mMinAlpha) * (p1 + position)就是(p1 - mMinAlpha)到0的变化
* （3）再加上一个mMinAlpha，就变为1到mMinAlpha的变化。
*/
float factor = mMinAlpha + (1 - mMinAlpha) * (1 + position);
page.setAlpha(factor);
page.setRotation(mMaxRotate * position);
//(4)position为width/2到width的变化
page.setPivotX(page.getWidth() * 0.5f * (1 - position));
page.setPivotY(page.getHeight());
else
//minAlpha到1的变化
float factor = mMinAlpha + (1 - mMinAlpha) * (1 - position);
page.setAlpha(factor);
page.setRotation(mMaxRotate * position);
page.setPivotX(page.getWidth() * 0.5f * (1 - position));
page.setPivotY(page.getHeight());
else
page.setAlpha(mMinAlpha);
page.setRotation(mMaxRotate);
page.setPivotX(0);
page.setPivotY(page.getHeight());
2.5item布局
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/colorAccent"
>
<ImageView
android:id="@+id/iv_page"
android:layout_width="wrap_content"
android:layout_height="260dp"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/tv"
android:textSize="16dp"
android:text="tag"
android:layout_gravity="center"
android:gravity="center"/>
</LinearLayout>
2.6Activity布局
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent"
android:layout_centerInParent="true"
android:background="#aadcff"
android:clipChildren="false">
<com.gdc.knowledge.highui.hightviewpager.MyViewPager
android:id="@+id/view_Pager"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginLeft="60dp"
android:layout_marginRight="60dp"
android:clipChildren="false"/>
<RadioGroup
android:id="@+id/radio_group"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal|bottom"
android:layout_marginBottom="10dp"
android:orientation="horizontal" />
</FrameLayout>
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