- 先看小红书的效果
小红书.GIF
说说思路
滚动效果用RecyclerView实现。RecyclerView有个smoothScrollToPosition方法，可以滚动到指定位置（有滚动效果，不是直接到指定位置），不了解的看这里RecycleView4种定位滚动方式演示。每一个Item是一张长图，这样首尾相接滚动起来（滚到无限远）就是无限循环的效果，然后再改变滚动的速度，完成。
public class MainActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//全屏
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_main);
mRecyclerView = findViewById(R.id.mRecyclerView);
mRecyclerView.setAdapter(new SplashAdapter(MainActivity.this));
mRecyclerView.setLayoutManager(new ScollLinearLayoutManager(MainActivity.this));
//smoothScrollToPosition滚动到某个位置（有滚动效果）
mRecyclerView.smoothScrollToPosition(Integer.MAX_VALUE / 2);
}
}
无限循环
将RecyclerView的Item数量设置成很大的值，用smoothScrollToPosition方法滚到很远的位置，就能实现这样的效果，很多banner轮播图的实现也是如此；
public class SplashAdapter extends RecyclerView.Adapter<SplashAdapter.ViewHolder> {
private int imgWidth;
public SplashAdapter(Context context) {
imgWidth = EasyUtil.getScreenWidth(context);
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_splash, parent, false);
return new ViewHolder(itemView);
}
@Override
public void onBindViewHolder(final ViewHolder holder, final int position) {
/* ViewGroup.LayoutParams lp = holder.item_bg.getLayoutParams();
lp.width = imgWidth;
lp.height =imgWidth*5;
holder.item_bg.setLayoutParams(lp);*/
}
@Override
public int getItemCount() {
return Integer.MAX_VALUE;
}
public class ViewHolder extends RecyclerView.ViewHolder {
ImageView item_bg;
public ViewHolder(final View itemView) {
super(itemView);
item_bg = itemView.findViewById(R.id.item_bg);
}
}
}
控制smoothScrollToPosition的滑动速度
参考RecyclerView调用smoothScrollToPosition() 控制滑动速度，修改MILLISECONDS_PER_INCH的值即可
/**
* 更改RecyclerView滚动的速度
*/
public class ScollLinearLayoutManager extends LinearLayoutManager {
private float MILLISECONDS_PER_INCH = 25f; //修改可以改变数据,越大速度越慢
private Context contxt;
public ScollLinearLayoutManager(Context context) {
super(context);
this.contxt = context;
}
@Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
LinearSmoothScroller linearSmoothScroller =
new LinearSmoothScroller(recyclerView.getContext()) {
@Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return ScollLinearLayoutManager.this
.computeScrollVectorForPosition(targetPosition);
}
@Override
protected float calculateSpeedPerPixel
(DisplayMetrics displayMetrics) {
return MILLISECONDS_PER_INCH / displayMetrics.density;
//返回滑动一个pixel需要多少毫秒
}
};
linearSmoothScroller.setTargetPosition(position);
startSmoothScroll(linearSmoothScroller);
}
//可以用来设置速度
public void setSpeedSlow(float x) {
//自己在这里用density去乘，希望不同分辨率设备上滑动速度相同
//0.3f是自己估摸的一个值，可以根据不同需求自己修改
MILLISECONDS_PER_INCH = contxt.getResources().getDisplayMetrics().density * 0.3f + (x);
}
}
图片宽度充满屏幕、高度按图片原始宽高比例自适应
@SuppressLint("AppCompatCustomView")
public class FitImageView extends ImageView {
public FitImageView(Context context) {
super(context);
}
public FitImageView(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
Drawable drawable = getDrawable();
if(drawable!=null){
int width = MeasureSpec.getSize(widthMeasureSpec);
int height = (int) Math.ceil((float) width * (float) drawable.getIntrinsicHeight() / (float) drawable.getIntrinsicWidth());
setMeasuredDimension(width, height);
}else{
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
}
这里需要注意的是、Item的根布局 android:layout_height=”wrap_content”，否则图片高度会受限
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.next.scrollimagedemo.view.FitImageView
android:id="@+id/item_bg"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:src="@mipmap/ww1" />
<!-- <ImageView
android:id="@+id/item_bg"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:src="@mipmap/ww2"
android:scaleType="centerCrop"/>-->
</android.support.constraint.ConstraintLayout>
使RecyclerView不能手指触碰滑动
加层View屏蔽掉事件就好了
<android.support.constraint.ConstraintLayout 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=".MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/mRecyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"></android.support.v7.widget.RecyclerView>
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#80000000"
android:clickable="true" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="80dp"
android:layout_marginTop="80dp"
app:layout_constraintTop_toTopOf="parent"
android:scaleType="centerInside"
android:src="@mipmap/slogan"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent" />
</android.support.constraint.ConstraintLayout>
完成效果
WW.GIF
Demo
github：https://github.com/forvv231/EasyScollImage
image.png
By the way
不要吐槽这背景图片、不喜欢、Demo代码里面还有别的(￣▽￣)~*
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