Android使用ontouch在画布上绘制矩形
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【中文标题】Android使用ontouch在画布上绘制矩形【英文标题】：Android Draw rectangle on canvas using ontouch 【发布时间】：2013-08-08 09:21:50 【问题描述】：我需要在画布上绘制一个矩形，其中包含来自 ontouch 事件的点。我得到了矩形形状，但是当我绘制另一个矩形时，前一个矩形消失了。我想我需要将矩形点存储在某个数组中。请给我一些建议。
到目前为止，我的代码如下。
视图类中的ontouch方法中的第一个
private void onTouchEvent(MotionEvent event)
xTouchCoordinate = event.getX();
yTouchCoordinate = event.getY();
if (event.getAction() == MotionEvent.ACTION_DOWN)
isActionUp = false;
pushState ();
startX = event.getX();
startY = event.getY();
else if (event.getAction() == MotionEvent.ACTION_UP)
isActionUp = true;
else if (event.getAction() == MotionEvent.ACTION_MOVE)
isActionUp = false;
if(mTouchMode == TouchModes.RECTANGLE )
updateRectPath(startX,startY , xTouchCoordinate , yTouchCoordinate);
而onDraw方法是
protected void onDraw(Canvas canvas)
ImageObject.setInteractiveMode(true);
int sc = canvas.save();
canvas.drawColor(Color.BLACK);
canvas.scale(mCanvasScale, mCanvasScale);
canvas.translate(mCanvasOffset.x, mCanvasOffset.y);
canvas.clipRect(mCanvasLimits);
canvas.drawColor(Color.WHITE);
if (currentState.drawGrid)
drawGridLines (canvas);
drawImages (canvas, true);
drawLines (canvas);
drawRectangles(canvas);
drawCircles(canvas);
drawOvals(canvas);
drawImages (canvas, false);
DrawRectangles 方法
private void drawRectangles(Canvas canvas)
try
if(path!=null)
if(mTouchMode == TouchModes.RECTANGLE)
finishPath(canvas);
catch(Exception e)
完成路径方法
void finishPath(Canvas canvas)
if(mTouchMode == TouchModes.RECTANGLE)
paint = new Paint();
paint.setAntiAlias(true);
paint.setDither(true);
paint.setStyle(Paint.Style.STROKE);
paint.setColor(currentState.currentColor);
paint.setFlags(Paint.DITHER_FLAG | Paint.ANTI_ALIAS_FLAG);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setStrokeWidth(currentStrokeWidth);
canvas.drawPath(path, paint);
void updateRectPath(float x1, float y1, float x2, float y2)
path.rewind();
x1 = x1 - mCanvasOffset.x;
y1 = y1 - mCanvasOffset.y;
x2 = x2 - mCanvasOffset.x;
y2 = y2 - mCanvasOffset.y;
translate(x1, y1);
Log.d ("x1 is "+x1, "y1 is "+y1);
if (x1 < x2 && y1 > y2)
path.addRect(x1, y2, x2, y1, Path.Direction.CW);
if (x1 < x2 && y1 < y2)
path.addRect(x1, y1, x2, y2, Path.Direction.CW);
if (x1 > x2 && y1 > y2)
path.addRect(x2, y2, x1, y1, Path.Direction.CW);
if (x1 > x2 && y1 < y2)
path.addRect(x2, y1, x1, y2, Path.Direction.CW);
【问题讨论】：
【参考方案1】：Hi if you have the source code of apidemos (or can find on internet), it has a fingerpaint example code. you can refer that: In any case i am pasting the code here..
/*
* Copyright (C) 2007 The android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.apis.graphics;
import android.content.Context;
import android.graphics.*;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
public class FingerPaint extends GraphicsActivity
implements ColorPickerDialog.OnColorChangedListener
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(new MyView(this));
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(0xFFFF0000);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(12);
mEmboss = new EmbossMaskFilter(new float[] 1, 1, 1 ,
0.4f, 6, 3.5f);
mBlur = new BlurMaskFilter(8, BlurMaskFilter.Blur.NORMAL);
private Paint mPaint;
private MaskFilter mEmboss;
private MaskFilter mBlur;
public void colorChanged(int color)
mPaint.setColor(color);
public class MyView extends View
private static final float MINP = 0.25f;
private static final float MAXP = 0.75f;
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
public MyView(Context c)
super(c);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh)
super.onSizeChanged(w, h, oldw, oldh);
mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
@Override
protected void onDraw(Canvas canvas)
canvas.drawColor(0xFFAAAAAA);
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
canvas.drawPath(mPath, mPaint);
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private void touch_start(float x, float y)
mPath.reset();
mPath.moveTo(x, y);
mX = x;
mY = y;
private void touch_move(float x, float y)
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE)
mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
mX = x;
mY = y;
private void touch_up()
mPath.lineTo(mX, mY);
// commit the path to our offscreen
mCanvas.drawPath(mPath, mPaint);
// kill this so we don't double draw
mPath.reset();
@Override
public boolean onTouchEvent(MotionEvent event)
float x = event.getX();
float y = event.getY();
switch (event.getAction())
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
return true;
private static final int COLOR_MENU_ID = Menu.FIRST;
private static final int EMBOSS_MENU_ID = Menu.FIRST + 1;
private static final int BLUR_MENU_ID = Menu.FIRST + 2;
private static final int ERASE_MENU_ID = Menu.FIRST + 3;
private static final int SRCATOP_MENU_ID = Menu.FIRST + 4;
@Override
public boolean onCreateOptionsMenu(Menu menu)
super.onCreateOptionsMenu(menu);
menu.add(0, COLOR_MENU_ID, 0, "Color").setShortcut('3', 'c');
menu.add(0, EMBOSS_MENU_ID, 0, "Emboss").setShortcut('4', 's');
menu.add(0, BLUR_MENU_ID, 0, "Blur").setShortcut('5', 'z');
menu.add(0, ERASE_MENU_ID, 0, "Erase").setShortcut('5', 'z');
menu.add(0, SRCATOP_MENU_ID, 0, "SrcATop").setShortcut('5', 'z');
/**** Is this the mechanism to extend with filter effects?
Intent intent = new Intent(null, getIntent().getData());
intent.addCategory(Intent.CATEGORY_ALTERNATIVE);
menu.addIntentOptions(
Menu.ALTERNATIVE, 0,
new ComponentName(this, NotesList.class),
null, intent, 0, null);
*****/
return true;
@Override
public boolean onPrepareOptionsMenu(Menu menu)
super.onPrepareOptionsMenu(menu);
return true;
@Override
public boolean onOptionsItemSelected(MenuItem item)
mPaint.setXfermode(null);
mPaint.setAlpha(0xFF);
switch (item.getItemId())
case COLOR_MENU_ID:
new ColorPickerDialog(this, this, mPaint.getColor()).show();
return true;
case EMBOSS_MENU_ID:
if (mPaint.getMaskFilter() != mEmboss)
mPaint.setMaskFilter(mEmboss);
else
mPaint.setMaskFilter(null);
return true;
case BLUR_MENU_ID:
if (mPaint.getMaskFilter() != mBlur)
mPaint.setMaskFilter(mBlur);
else
mPaint.setMaskFilter(null);
return true;
case ERASE_MENU_ID:
mPaint.setXfermode(new PorterDuffXfermode(
PorterDuff.Mode.CLEAR));
return true;
case SRCATOP_MENU_ID:
mPaint.setXfermode(new PorterDuffXfermode(
PorterDuff.Mode.SRC_ATOP));
mPaint.setAlpha(0x80);
return true;
return super.onOptionsItemSelected(item);
【讨论】：
嗨，如果这个答案符合您的目的，请接受它，以便其他人可以知道正确的答案并使用它..谢谢以上是关于Android使用ontouch在画布上绘制矩形的主要内容，如果未能解决你的问题，请参考以下文章
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