EasyScollImage

Introduction: 仿小红书登录页 长图片背景自动滚动效果
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仿小红书登录页 长图片背景滚动效果

  • 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 {

    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](https://blog.csdn.net/a86261566/article/details/50906456),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**
<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"/>-->


- 使 RecyclerView 不能手指触碰滑动
加层 View 屏蔽掉事件就好了
<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" />

```

  • 完成效果

WW.GIF


Demo github:https://github.com/forvv231/EasyScollImage

apk:https://fir.im/gfdj

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( ̄▽ ̄)~*

点个赞吧 年初给自己定了今年存 3 万块钱的目标,刚才自己算了一下,还差 8 万…

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