How to draw multiple lines with finger? (Android)

Question

I have tried to draw multiple lines like this:

`

l1 = new Path();

l2 = new Path();
l3 = new Path();
l4 = new Path();`
---
`mPathList.add(l1...l4);`
---

    `public void onDraw(Canvas canvas) {
    ...

for (Path path : mPathList) {
canvas.drawPath(path, mOverlayPaint);

    }
    ...
    }`

    ---
    `case MotionEvent.ACTION_MOVE:
    int X = (int)me.getRawX();
    int Y = (int)me.getRawY();

    l1.moveTo(X, Y);
    l2.moveTo(X + 5, Y);
    l3.moveTo(X + 10, Y);
    l4.moveTo(X + 15, Y);
    break;`

But when I'm trying to draw something, FPS will slowly decrease. Any ideas how to make it works fine? P.S. Sorry for my English, please

Answer 1

What you need to do is store the lines inside an arraylist and then read the arraylist onDraw(). try this code for your View Class:

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import java.util.ArrayList;

class Line {
  float startX, startY, stopX, stopY, 
  float joinX, joinY = 0;
  public Line(float startX, float startY, float stopX, float stopY) {
    this.startX = startX;
    this.startY = startY;
    this.stopX = stopX;
    this.stopY = stopY;
  }
  public Line(float startX, float startY) { // for convenience
    this(startX, startY, startX, startY);
  }
}

public class DrawView extends View {
  Paint paint = new Paint();
  ArrayList<Line> lines = new ArrayList<Line>();

  public DrawView(Context context, AttributeSet attrs) {
    super(context, attrs);

    paint.setAntiAlias(true);
    paint.setStrokeWidth(6f);
    paint.setColor(Color.BLACK);
    paint.setStyle(Paint.Style.STROKE);
    paint.setStrokeJoin(Paint.Join.ROUND);
  }

  @Override
  protected void onDraw(Canvas canvas) {
    for (Line l : lines) {
      canvas.drawLine(l.startX, l.startY, l.stopX, l.stopY, paint);
    }
  }

  @Override
  public boolean onTouchEvent(MotionEvent event) {

    if (event.getAction() == MotionEvent.ACTION_DOWN) {
      if (joinX <= 0 || joinY <= 0) lines.add(new Line(event.getX(), event.getY()));
      else lines.add(new Line(joinX, joinY);
      return true;
    }
    else if ((event.getAction() == MotionEvent.ACTION_MOVE) &&
        lines.size() > 0) {
      Line current = lines.get(lines.size() - 1);
      current.stopX = event.getX();
      current.stopY = event.getY();
      Invalidate();
      return true;
    }
    else if ((event.getAction() == MotionEvent.ACTION_UP) &&
        lines.size() > 0 {
      Line current = lines.get(lines.size() - 1);
      current.stopX = event.getX();
      current.stopY = event.getY();
      joinX = event.getX();
      joinY = event.getY();
      Invalidate();
      return true;
    }
    else {
      return false;
    }
  }
}