Android觸控事件實現筆觸畫布
任何View都有觸控事件,經常在自定義控制元件時重寫setOnTouchListener
本篇通過手繪圖片來講述這個知識點
本篇分為三個等級:一覽圖:
直線 | 曲線 | 筆觸 |
---|---|---|
LEVEL1.png |
LEVEL2.png |
LEVER3.png |
LEVEL1:基礎實現
在Activity中通過一個全屏的Bitmap建立的Canvas繪製
為ImageView新增觸控事件監聽。
1.成員變數
ImageView mIdIvShow; float downX = 0; float downY = 0; float upX = 0; float upY = 0; private Canvas mCanvas; private Paint mPaint;
2.建立畫布
//獲取螢幕尺寸 Point point = new Point(); getWindowManager().getDefaultDisplay().getSize(point); //建立一個和螢幕一樣大的Bitmap Bitmap bitmap = Bitmap.createBitmap(point.x, point.y, Bitmap.Config.ARGB_8888); //建立Canvas物件 mCanvas = new Canvas(bitmap); mPaint = new Paint(Paint.ANTI_ALIAS_FLAG); mPaint.setStrokeWidth(10); mPaint.setColor(Color.RED); //將bitmap用ImageView展示 mIdIvShow.setImageBitmap(bitmap);
3.監聽事件
mIdIvShow.setOnTouchListener((v, event) -> { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: downX = event.getX(); downY = event.getY(); L.d("按下:(" + downX + "," + downY + ")" + L.l()); break; case MotionEvent.ACTION_CANCEL: break; case MotionEvent.ACTION_MOVE: break; case MotionEvent.ACTION_UP: upX = event.getX(); upY = event.getY(); L.d("抬起:(" + upX + "," + upY + ")" + L.l()); mCanvas.drawLine(downX, downY, upX, upY, mPaint); mIdIvShow.invalidate();//更新檢視 break; } return true; }); }
升級版:LEVER2
LEVEL2.png
mIdIvShow.setOnTouchListener((v, event) -> { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: downX = event.getX(); downY = event.getY(); break; case MotionEvent.ACTION_CANCEL: break; case MotionEvent.ACTION_MOVE: upX = event.getX(); upY = event.getY(); mCanvas.drawLine(downX, downY, upX, upY, mPaint); mIdIvShow.invalidate(); //更新點位 downY = upY; downX = upX; break; case MotionEvent.ACTION_UP: //抬起點Y>1100,清除筆跡 if (upY > 1100) { Paint paint = new Paint(); paint.setColor(Color.WHITE); mCanvas.drawRect(0, 0, mPoint.x, mPoint.y, paint); } break; } return true; });
再升級版:LEVER3
筆觸根據繪製的速度動態改變畫筆粗細
LEVER3.png
float movingX = 0; float movingY = 0; private long lastTimestamp = 0L;//最後一次的時間戳
mIdIvShow.setOnTouchListener((view, event) -> { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: lastTimestamp = System.currentTimeMillis(); downX = event.getX(); downY = event.getY(); break; case MotionEvent.ACTION_CANCEL: break; case MotionEvent.ACTION_MOVE: movingX = event.getX(); movingY = event.getY(); long curTimestamp = System.currentTimeMillis(); //計算時間差 long detaT = curTimestamp - lastTimestamp; //計算距離差 float detaS = Logic.disPos2d(movingX, movingY, downX, downY); //由於速度是 px/ms double v = detaS / detaT; //速度轉化為畫筆寬度的等式 float width = 14/(float)v; L.d(width + L.l()); //限制極值情況 if ((width > 0) && width < 30) { mPaint.setStrokeWidth(width); } mCanvas.drawLine(downX, downY, movingX, movingY, mPaint); mIdIvShow.invalidate(); downX = movingX; downY = movingY; lastTimestamp = curTimestamp;//更新時間 movePos.add(new PointF(event.getX(), event.getY())); break; } return true; });
拓展
1.其中可以改變求寬度的等式實現不同的筆觸:如
float width = (float) Math.log10(v) * 40;
LEVER3+.png
2.在圖片上繪畫
//圖片原型 Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.iv_500x400); //圖片副本 Bitmap mNewBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), bitmap.getConfig()); //用副本生成Canvas mCanvas = new Canvas(mNewBitmap); mPaint = new Paint(Paint.ANTI_ALIAS_FLAG); mPaint.setStrokeCap(Paint.Cap.ROUND);//直線圓頭 mCanvas.drawBitmap(bitmap, new Matrix(), mPaint); mPaint.setStrokeWidth(10); mPaint.setColor(Color.parseColor("#88164BE6")); //設定副本圖片到ImageView mIdIvShow.setImageBitmap(mNewBitmap);
拓展2.png
後記:捷文規範
1.本文成長記錄及勘誤表
專案原始碼 | 日期 | 備註 |
---|---|---|
V0.1--無 | 2018-10-30 | ofollow,noindex">Android觸控事件實現筆觸畫布 |
2.更多關於我
筆名 | 微信 | 愛好 | |
---|---|---|---|
張風捷特烈 | 1981462002 | zdl1994328 | 語言 |
我的github | 我的簡書 | 我的CSDN | 個人網站 |
3.宣告
1----本文由張風捷特烈原創,轉載請註明
2----歡迎廣大程式設計愛好者共同交流
3----個人能力有限,如有不正之處歡迎大家批評指證,必定虛心改正
4----看到這裡,我在此感謝你的喜歡與支援