Android仿小红书图片自动滚动效果

龙旋

共 6574字,需浏览 14分钟

 ·

2021-09-17 04:00

今天来跟大家探讨一下,如何实现长图片自动循环滚动效果(仿小红书),板凳准备好,来围观啦!

效果图


实现思路

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,就可以了。
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); }}

1、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);        }    }}

2、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); }
}

3、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); }    }}

4、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>

5、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


到这里就结束啦。
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