Android開發滯留在繪畫/繪圖

Question

我想要完成的事情很簡單。製作一個非常基本的和/或原始的繪圖應用程序。沒有改變畫筆大小，沒有改變顏色或類似的東西，只是一個簡單的繪圖應用程序，就像你在一張簡單的紙片上繪製一樣。

我知道畫布和油漆，但不知道如何實現我提到的免費繪圖概念。任何幫助將大大apprechiated。

@Override 
    protected void onDraw(Canvas canvas) { 
    Paint p = new Paint(); 

    p.setColor(Color.BLUE); 

    int width = getWidth(); 
    int height = getHeight(); 

    canvas.drawLine(0, 0, width, height, p); 
} 

Answer 1

您的課程必須擴展視圖。你重寫onDraw（畫布）來繪製路徑。您重寫onTouch（event）並調用invalidate刷新繪製。您使用路徑繪製。

public class MainActivity extends Activity { 

DrawingView dv ; 
RelativeLayout rl; 
private Paint  mPaint; 
private DrawingManager mDrawingManager=null; 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    dv = new DrawingView(this); // custom view 
    setContentView(dv); 
    mPaint = new Paint(); 
    mPaint.setAntiAlias(true); 
    mPaint.setDither(true); 
    mPaint.setColor(Color.GREEN); 
    mPaint.setStyle(Paint.Style.STROKE); 
    mPaint.setStrokeJoin(Paint.Join.ROUND); 
    mPaint.setStrokeCap(Paint.Cap.ROUND); 
    mPaint.setStrokeWidth(12); // paint thickness 
} 

public class DrawingView extends View { 

     public int width; 
     public int height; 
     private Bitmap mBitmap; 
     private Canvas mCanvas; 
     private Path mPath; 
     private Paint mBitmapPaint; 
     Context context; 
     private Paint circlePaint; 
     private Path circlePath; 

     public DrawingView(Context c) { 
     super(c); 
     context=c; 
     mPath = new Path(); // path used to draw 
     mBitmapPaint = new Paint(Paint.DITHER_FLAG); 

     circlePaint = new Paint(); 

     circlePath = new Path(); 
     circlePaint.setAntiAlias(true); 
     circlePaint.setColor(Color.BLUE); 
     circlePaint.setStyle(Paint.Style.STROKE); 
     circlePaint.setStrokeJoin(Paint.Join.MITER); 
     circlePaint.setStrokeWidth(4f); 
        // draw a circle when user touch and move. 
     } 

     @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) { 
     super.onDraw(canvas); 

     canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);  
     canvas.drawPath(mPath, mPaint); // draw the path 
     canvas.drawPath(circlePath, circlePaint); //draw the circle 
     } 

     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; 

      circlePath.reset(); 
      circlePath.addCircle(mX, mY, 30, Path.Direction.CW); 
     } 
     } 
     private void touch_up() { 
     mPath.lineTo(mX, mY); 
     circlePath.reset(); 
     // 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) { // touch events 
     float x = event.getX(); 
     float y = event.getY(); 

     switch (event.getAction()) { 
      case MotionEvent.ACTION_DOWN: 
       touch_start(x, y); 
       invalidate(); // invalidate to refresh 
       break; 
      case MotionEvent.ACTION_MOVE: 
       touch_move(x, y); 
       invalidate(); 
       break; 
      case MotionEvent.ACTION_UP: 
       touch_up(); 
       invalidate(); 
       break; 
     } 
     return true; 
     } 
     } 

}

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