Android RecyclerView ItemDecoration timeline（一）

超、凢脫俗 2023-10-18 12:48 8阅读 0赞

package zhangphil.book;
    
    import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.Color;
    import android.graphics.Paint;
    import android.graphics.Rect;
    import android.graphics.drawable.ColorDrawable;
    import android.graphics.drawable.Drawable;
    import android.os.Bundle;
    import android.support.annotation.NonNull;
    import android.support.v4.content.ContextCompat;
    import android.support.v7.app.AppCompatActivity;
    import android.support.v7.widget.LinearLayoutManager;
    import android.support.v7.widget.RecyclerView;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.TextView;
    
    public class MainActivity extends AppCompatActivity {
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            RecyclerView mRecyclerView = findViewById(R.id.recycler_view);
    
            LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getApplicationContext());
            linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
            mRecyclerView.setLayoutManager(linearLayoutManager);
    
            RecyclerViewAdapter adapter = new RecyclerViewAdapter();
            mRecyclerView.setAdapter(adapter);
    
            RVItemDecoration mRVItemDecoration = new RVItemDecoration(getApplicationContext());
            mRecyclerView.addItemDecoration(mRVItemDecoration);
        }
    
        private class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewHolder> {
            @NonNull
            @Override
            public RecyclerViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View view = LayoutInflater.from(getApplicationContext()).inflate(android.R.layout.simple_list_item_1, parent, false);
                RecyclerViewHolder holder = new RecyclerViewHolder(view);
                return holder;
            }
    
            @Override
            public void onBindViewHolder(@NonNull RecyclerViewHolder holder, int position) {
                holder.text1.setText(position + "");
            }
    
            @Override
            public int getItemCount() {
                return Integer.MAX_VALUE;
            }
        }
    
        private class RecyclerViewHolder extends RecyclerView.ViewHolder {
            public TextView text1;
    
            public RecyclerViewHolder(View itemView) {
                super(itemView);
                text1 = itemView.findViewById(android.R.id.text1);
            }
        }
    
        private class RVItemDecoration extends RecyclerView.ItemDecoration {
            private Drawable mDrawable;
    
            //轴线距离左侧的距离，单位pix。
            private int marginLeft = 20;
    
            //轴线的宽度，单位pix。
            private int lineSize = 10;
    
            private Paint mPaint;
    
            public RVItemDecoration(Context context) {
                mPaint = new Paint();
                mPaint.setAntiAlias(true);
                mPaint.setColor(Color.RED);
    
                mDrawable = new ColorDrawable(ContextCompat.getColor(getApplicationContext(), android.R.color.holo_blue_light));
            }
    
            @Override
            public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
                canvas.save();
    
                int childCount = parent.getChildCount();
                for (int i = 0; i < childCount; i++) {
                    View child = parent.getChildAt(i);
    
                    //先画线。
                    mDrawable.setBounds(marginLeft, child.getTop(), marginLeft + lineSize, child.getBottom());
                    mDrawable.draw(canvas);
    
                    //后画覆盖在线上的圆球。
                    canvas.drawCircle(marginLeft + lineSize / 2, (child.getTop() + child.getBottom()) / 2, (lineSize + marginLeft) / 2, mPaint);
                }
    
                canvas.restore();
            }
    
            /**
             * outRect.set()函数相当于给RecyclerView的每一个item的View四周设置margin值。
             * 此处的margin值不同于onDraw里面的margin，onDraw里面给mDrawable设置的margin，仅仅是针对分割条而言。
             *
             * @param outRect
             * @param view
             * @param parent
             * @param state
             */
            @Override
            public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
                outRect.set((marginLeft + lineSize) * 2, 0, 0, 0);
    
                //测试。给RecyclerView的每一个item设置一个浅灰色背景。
                //便于观察绘制结果。
                view.setBackgroundColor(Color.LTGRAY);
            }
        }
    }

so：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poYW5ncGhpbA_size_16_color_FFFFFF_t_70][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poYW5ncGhpbA_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20181218135550687.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poYW5ncGhpbA==,size_16,color_FFFFFF,t_70