Android RecyclerView ItemDecoration timeline（一）
16lz
2021-01-23
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 { @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：
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