canvas通俗的說就是一張畫布,我們可以使用畫筆paint,在其上面畫任意的圖形。
方法:
//繪製區域,參數一爲RectF一個區域
drawRect(RectF rect, Paint paint)
//繪製一個路徑,參數一爲Path路徑對象
drawPath(Path path, Paint paint)
//貼圖,參數一就是我們常規的Bitmap對象,參數二是源區域(這裏是bitmap),參數三是目標區域
(應該在canvas的位置和大小),參數四是Paint畫刷對象,因爲用到了縮放和拉伸的可能,當原始
Rect不等於目標Rect時性能將會有大幅損失。
drawBitmap(Bitmap bitmap, Rect src, Rect dst, Paint paint)
//畫線,參數一起始點的x軸位置,參數二起始點的y軸位置,參數三終點的x軸水平位置,
參數四y軸垂直位置,最後一個參數爲Paint 畫刷對象。
drawLine(float startX, float startY, float stopX, float stopY, Paintpaint)
//畫點,參數一水平x軸,參數二垂直y軸,第三個參數爲Paint對象。
drawPoint(float x, float y, Paint paint)
//渲染文本,Canvas類除了上面的還可以描繪文字,參數一是String類型的文本,參數二x軸,
參數三y軸,參數四是Paint對象。
drawText(String text, float x, floaty, Paint paint)
//畫橢圓,參數一是掃描區域,參數二爲paint對象;
drawOval(RectF oval, Paint paint)
// 繪製圓,參數一是中心點的x軸,參數二是中心點的y軸,參數三是半徑,參數四是paint對象;
//畫弧,參數一是RectF對象,一個矩形區域橢圓形的界限用於定義在形狀、大小、電弧,參數二是
起始角(度)在電弧的開始,參數三掃描角(度)開始順時針測量的,參數四是如果這是真的話,包括
橢圓中心的電弧,並關閉它,如果它是假這將是一個弧線,參數五是Paint對象;
drawArc(RectF oval, float startAngle, float sweepAngle, boolean useCenter, Paint paint)
接下來就要開始畫了。還需要工具Paint,path
Paint ,就是畫筆,我們new paint();等到一隻畫筆,然後設置它的一些屬性。
Paint類常用方法:
setARGB(int a, int r, int g, int b) // 設置 Paint對象顏色,參數一爲alpha透明值
setAlpha(int a) // 設置alpha不透明度,範圍爲0~255
setAntiAlias(boolean aa) // 是否抗鋸齒
setColor(int color) // 設置顏色,這裏Android內部定義的有Color類包含了一些常見顏色定義
setTextScaleX(float scaleX) // 設置文本縮放倍數,1.0f爲原始
setTextSize(float textSize) // 設置字體大小
setUnderlineText(booleanunderlineText) // 設置下劃線
setStyle(Style.STROKE)//設置畫筆空心
- public class DrawviewActivity extends Activity {
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- // set DrawView's width and height
- Display d = getWindowManager().getDefaultDisplay();
- DrawView dv = new DrawView(this);
- dv.width = d.getWidth();
- dv.height = d.getHeight();
- setContentView(dv);
- }
- class DrawView extends View {
- public float width;
- public float height;
- private Paint mpaint;
- public DrawView(Context context) {
- super(context);
- mpaint = new Paint();
- mpaint.setColor(Color.RED);
- mpaint.setAntiAlias(true);
- }
- @Override
- protected void onDraw(Canvas canvas) {
- // TODO Auto-generated method stub
- super.onDraw(canvas);
- // drawtext
- canvas.save();
- mpaint.setTextSize(30);
- canvas.drawText("hello honjane", 20, 20, mpaint);
- canvas.restore();
- // drawRect
- canvas.save();
- RectF r = new RectF(40, 40, 60, 60);
- mpaint.setColor(Color.BLUE);
- canvas.drawRect(r, mpaint);
- canvas.restore();
- canvas.save();
- mpaint.setColor(Color.BLUE);
- canvas.drawRect(65, 40, 85, 60, mpaint);
- canvas.restore();
- // drawCircle
- canvas.save();
- mpaint.setStyle(Style.STROKE);
- canvas.drawCircle(width / 2, height / 2, 100, mpaint);
- canvas.restore();
- // drawArc
- canvas.save();
- RectF oval1 = new RectF(150, 300, 180, 400);
- canvas.drawArc(oval1, 180, 250, false, mpaint);// 小弧形
- oval1.set(300, 300, 600, 780);
- canvas.drawArc(oval1, 230, 170, false, mpaint);
- oval1.set(200, 300, 500, 780);
- canvas.drawArc(oval1, 230, 170, true, mpaint);
- canvas.restore();
- // 三角形
- canvas.save();
- mpaint.setStyle(Style.FILL);
- Path p = new Path();
- p.moveTo(80, 100);
- p.lineTo(140, 300);
- p.lineTo(20, 300);
- p.close();
- canvas.drawPath(p, mpaint);
- canvas.restore();
- canvas.save();
- mpaint.setStyle(Paint.Style.FILL);// 充滿
- mpaint.setColor(Color.LTGRAY);
- mpaint.setAntiAlias(true);// 設置畫筆的鋸齒效果
- canvas.drawText("畫圓角矩形:", 10, 260, mpaint);
- RectF oval3 = new RectF(80, 260, 200, 300);// 設置個新的長方形
- canvas.drawRoundRect(oval3, 20, 15, mpaint);// 第二個參數是x半徑,第三個參數是y半徑
- canvas.restore();
- // 可變色的
- canvas.save();
- Shader shader = new LinearGradient(0, 0, 100, 100, new int[] {
- Color.BLACK, Color.CYAN, Color.DKGRAY, Color.GRAY }, null,
- Shader.TileMode.MIRROR);
- mpaint.setShader(shader);
- RectF oval2 = new RectF(250, 100, 450, 300);
- canvas.drawArc(oval2, 200, 130, true, mpaint);
- canvas.restore();
- //畫圖片
- canvas.save();
- Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
- canvas.drawBitmap(bitmap, 250,360, mpaint);
- canvas.restore();
- }
- }
- }