Android學習之繪圖入門

Android的繪圖繼承於View組件，重寫onDraw(Canvas canvas) 方法時涉及一個繪圖API: Canvas 代表了依附於指定View的畫布，並且提供了很多繪制方法。

Canvas提供的方法還涉及一個API: Paint ,Paint代表了Canvas上的畫筆，主要用於設置繪制風格，畫筆顏色，粗細，填充風格等。

Path代表任意多條直線連接而成的任意圖形，當Canvas根據Path繪制圖形時，它可以繪制出任意形狀的圖形。

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.view.View;

public class MyView extends View {
	public MyView(Context context, AttributeSet set) {
		super(context, set);
	}

	@Override
	// 重寫該方法，進行繪圖
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		// 把整張畫布繪制成白色
		canvas.drawColor(Color.WHITE);
		Paint paint = new Paint();
		// 去鋸齒
		paint.setAntiAlias(true);
		paint.setColor(Color.BLUE);
		paint.setStyle(Paint.Style.STROKE);
		paint.setStrokeWidth(3);
		// 繪制圓形
		canvas.drawCircle(40, 40, 30, paint);
		// 繪制正方形
		canvas.drawRect(10, 80, 70, 140, paint);
		// 繪制矩形
		canvas.drawRect(10, 150, 70, 190, paint);
		RectF re1 = new RectF(10, 200, 70, 230);
		// 繪制圓角矩形
		canvas.drawRoundRect(re1, 15, 15, paint);
		RectF re11 = new RectF(10, 240, 70, 270);
		// 繪制橢圓
		canvas.drawOval(re11, paint);
		// 定義一個Path對象，封閉成一個三角形。
		Path path1 = new Path();
		path1.moveTo(10, 340);
		path1.lineTo(70, 340);
		path1.lineTo(40, 290);
		path1.close();
		// 根據Path進行繪制，繪制三角形
		canvas.drawPath(path1, paint);
		// 定義一個Path對象，封閉成一個五角形。
		Path path2 = new Path();
		path2.moveTo(26, 360);
		path2.lineTo(54, 360);
		path2.lineTo(70, 392);
		path2.lineTo(40, 420);
		path2.lineTo(10, 392);
		path2.close();
		// 根據Path進行繪制，繪制五角形
		canvas.drawPath(path2, paint);
		// ----------設置填充風格後繪制----------
		paint.setStyle(Paint.Style.FILL);
		paint.setColor(Color.RED);
		canvas.drawCircle(120, 40, 30, paint);
		// 繪制正方形
		canvas.drawRect(90, 80, 150, 140, paint);
		// 繪制矩形
		canvas.drawRect(90, 150, 150, 190, paint);
		RectF re2 = new RectF(90, 200, 150, 230);
		// 繪制圓角矩形
		canvas.drawRoundRect(re2, 15, 15, paint);
		RectF re21 = new RectF(90, 240, 150, 270);
		// 繪制橢圓
		canvas.drawOval(re21, paint);
		Path path3 = new Path();
		path3.moveTo(90, 340);
		path3.lineTo(150, 340);
		path3.lineTo(120, 290);
		path3.close();
		// 繪制三角形
		canvas.drawPath(path3, paint);
		Path path4 = new Path();
		path4.moveTo(106, 360);
		path4.lineTo(134, 360);
		path4.lineTo(150, 392);
		path4.lineTo(120, 420);
		path4.lineTo(90, 392);
		path4.close();
		// 繪制五角形
		canvas.drawPath(path4, paint);
		// ----------設置漸變器後繪制----------
		// 為Paint設置漸變器
		Shader mShader = new LinearGradient(0, 0, 40, 60, new int[] {
				Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW }, null,
				Shader.TileMode.REPEAT);
		paint.setShader(mShader);
		// 設置陰影
		paint.setShadowLayer(45, 10, 10, Color.GRAY);
		// 繪制圓形
		canvas.drawCircle(200, 40, 30, paint);
		// 繪制正方形
		canvas.drawRect(170, 80, 230, 140, paint);
		// 繪制矩形
		canvas.drawRect(170, 150, 230, 190, paint);
		RectF re3 = new RectF(170, 200, 230, 230);
		// 繪制圓角矩形
		canvas.drawRoundRect(re3, 15, 15, paint);
		RectF re31 = new RectF(170, 240, 230, 270);
		// 繪制橢圓
		canvas.drawOval(re31, paint);
		Path path5 = new Path();
		path5.moveTo(170, 340);
		path5.lineTo(230, 340);
		path5.lineTo(200, 290);
		path5.close();
		// 根據Path進行繪制，繪制三角形
		canvas.drawPath(path5, paint);
		Path path6 = new Path();
		path6.moveTo(186, 360);
		path6.lineTo(214, 360);
		path6.lineTo(230, 392);
		path6.lineTo(200, 420);
		path6.lineTo(170, 392);
		path6.close();
		// 根據Path進行繪制，繪制五角形
		canvas.drawPath(path6, paint);
		// ----------設置字符大小後繪制----------
		paint.setTextSize(24);
		paint.setShader(null);
		// 繪制7個字符串
		canvas.drawText(getResources().getString(R.string.circle), 240, 50,paint);
		canvas.drawText(getResources().getString(R.string.square), 240, 120,paint);
		canvas.drawText(getResources().getString(R.string.rect), 240, 175,paint);
		canvas.drawText(getResources().getString(R.string.round_rect), 230,220, paint);
		canvas.drawText(getResources().getString(R.string.oval), 240, 260,paint);
		canvas.drawText(getResources().getString(R.string.triangle), 240, 325,paint);
		canvas.drawText(getResources().getString(R.string.pentagon), 240, 390,paint);
	}
}