问题描述
限时送ChatGPT账号..好的,我正在尝试制作一个使用 linedrawview 的程序.当用户启动一个触摸事件(动作 DOWN)时,它会获取当前的 x 和 y 并将它们存储在变量中.然后当用户拖动他们的手指时,会画一条线并以橡皮筋的方式动画.最后,当用户放手(动作 UP)时,就创建了该行.我在这方面遇到了很多麻烦,需要一些帮助.到目前为止,我的 LineDrawView.java 代码:
Ok, I'm trying to make a program that utilizes a linedrawview. When the user starts a touch event(action DOWN), it gets the current x and y and stores them in variables. Then when the user drags their finger around, a line is drawn and animates in a rubber band way. Finally, when the user lets go (action UP), the line is created. I'm having a lot of trouble with this and would like some assistance. My code so far for LineDrawView.java:
// Project: Java2LineDrawEx
// File: LineDrawView.java
// Date: 4/9/13
// Author: Joshua Lefelhocz
// Description: custom view to draw lines on
package com.lcc.java2lab11lefelhocz;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.View;
// Notice this class extends View
public class LineDrawView extends View
{
// This view's bounds
private int xMin = 0;
private int xMax;
private int yMin = 0;
private int yMax;
private float currentX;
private float currentY;
// Paint object
private Paint paintFill;
// constructor
public LineDrawView(Context context)
{
// call the super class constructor
super(context);
// The Paint class holds the style and color information about how to draw geometries, text and bitmaps.
// For efficiency create the paint objects in the constructor, not in draw
// paint.setStrokeWidth(10); // works on lines
// You can change the color of Paint without effecting objects already drawn
// You can NOT change the style of Paint without effecting objects already drawn
// The Style, TextSize apply to all objects drawn with the paint.
// Create a default Paint object Style=Fill
paintFill = new Paint();
// set the background color when the view is created
this.setBackgroundColor(Color.LTGRAY);
}
// Called to draw the view. Also called by invalidate().
@Override
protected void onDraw(Canvas canvas)
{
// canvas.drawColor(Color.LTGRAY); // this works in onDraw to set the background color
// Draw a Red Diagonal line from upper left corner to bottom right corner
paintFill.setColor(Color.RED);
canvas.drawLine(xMin, yMin, xMax, yMax, paintFill);
// draw a blue line 10 pixels wide horizontal across the center.
paintFill.setColor(Color.BLUE);
paintFill.setStrokeWidth(10);
canvas.drawLine(xMin, yMax/2, xMax, yMax/2, paintFill);
// draw a yellow line 20 pixels wide vertical across the center.
paintFill.setColor(Color.YELLOW);
paintFill.setStrokeWidth(20);
canvas.drawLine(xMax/2, yMin, xMax/2, yMax, paintFill);
}
// Called when the view is first created or its size changes.
@Override
public void onSizeChanged(int width, int height, int oldWidth, int oldHeight)
{
// Set the view bounds
xMax = width-1;
yMax = height-1;
}
public boolean onTouchEvent(MotionEvent event)
{
currentX = event.getX();
currentY = event.getY();
switch(event.getAction())
{
case MotionEvent.ACTION_DOWN:
float startX = currentX;
float startY = currentY;
case MotionEvent.ACTION_MOVE:
float endX =
case MotionEvent.ACTION_UP:
return super.onTouchEvent(event);
}
return super.onTouchEvent(event);
}
}
推荐答案
好的,我发现:确保设置开始位置 x 和 y,如下所示:
Okay, I found out: Make sure to set the start position x and y, like this:
currentXExample = event.getX();currentYExample = event.getY();
currentXExample = event.getX(); currentYExample = event.getY();
exampleStartX = currentXExample;exampleStartY = currentYExample;
exampleStartX = currentXExample; exampleStartY = currentYExample;
exampleEndX = currentXExample;
exampleEndX = currentXExample;
exampleEndY = currentYExample;
exampleEndY = currentYExample;
您可以将其排除在 Up 事件之外,但切勿将其排除在 MOVE 事件之外,否则它将无法工作.
You can leave it out of the Up event, but never leave it out of the MOVE event or it will not work.
LineDrawView.java
LineDrawView.java
// Project: Java2Lab
// File: LineDrawView.java
// Date: 4/9/13
// Author: Joshua Lefelhocz
// Description: custom view to draw lines on
package com.lcc.java2lab11lefelhocz;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.View;
// Notice this class extends View
public class LineDrawView extends View
{
// This view's bounds
private int xMin = 0;
private int xMax;
private int yMin = 0;
private int yMax;
private float currentX;
private float currentY;
private float startX;
private float endX;
private float startY;
private float endY;
// Paint object
private Paint paintFill;
// constructor
public LineDrawView(Context context)
{
// call the super class constructor
super(context);
// The Paint class holds the style and color information about how to draw geometries, text and bitmaps.
// For efficiency create the paint objects in the constructor, not in draw
// paint.setStrokeWidth(10); // works on lines
// You can change the color of Paint without effecting objects already drawn
// You can NOT change the style of Paint without effecting objects already drawn
// The Style, TextSize apply to all objects drawn with the paint.
// Create a default Paint object Style=Fill
paintFill = new Paint();
// set the background color when the view is created
this.setBackgroundColor(Color.LTGRAY);
}
// Called to draw the view. Also called by invalidate().
@Override
protected void onDraw(Canvas canvas)
{
//canvas.drawColor(Color.LTGRAY); // this works in onDraw to set the background color
// Draw a Red Diagonal line from upper left corner to bottom right corner
paintFill.setColor(Color.BLACK);
canvas.drawLine(startX, startY, endX, endY, paintFill);
}
// Called when the view is first created or its size changes.
@Override
public void onSizeChanged(int width, int height, int oldWidth, int oldHeight)
{
// Set the view bounds
xMax = width-1;
yMax = height-1;
}
public boolean onTouchEvent(MotionEvent event)
{
currentX = event.getX();
currentY = event.getY();
switch(event.getAction())
{
case MotionEvent.ACTION_DOWN:
startX = currentX;
startY = currentY;
return true;
case MotionEvent.ACTION_MOVE:
endX = currentX;
endY = currentY;
invalidate();
return true;
case MotionEvent.ACTION_UP:
return true;
}
return super.onTouchEvent(event);
}
}
这篇关于使用 ontouchevent 绘制橡皮筋线的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
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