Canvas Paint 简单的使用示例

自定义的 View 文件的代码如下：

package com.toby.personal.testlistview;

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.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by zhaodongshuang on 2017/4/9.
 */

public class TestView01 extends View {

    private Paint paint = null;

    private RectF rectF0 = null;
    private RectF rectF1 = null;
    private RectF rectF2 = null;
    private RectF rectF3 = null;
    private RectF rectF4 = null;
    private RectF rectF5 = null;

    private Path path1 = null;
    private Path path2 = null;
    private Path path3 = null;
    private Path path4 = null;
    private Path path5 = null;
    private Path path6 = null;

    private Shader shader = null;

    public TestView01(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);

        paint = new Paint();


        rectF0 = new RectF(10, 200, 70, 230);
        rectF1 = new RectF(10, 240, 70, 270);

        rectF2 = new RectF(90, 200, 150, 230);
        rectF3 = new RectF(90, 240, 150, 270);

        rectF4 = new RectF(170, 200, 230, 230);
        rectF5 = new RectF(170, 240, 230, 270);

        // 定义一个三角形
        path1 = new Path();
        path1.moveTo(10, 340);
        path1.lineTo(70, 340);
        path1.lineTo(40, 290);
        path1.close();

        path3 = new Path();
        path3.moveTo(90, 340);
        path3.lineTo(150, 340);
        path3.lineTo(120, 290);
        path3.close();

        path5 = new Path();
        path5.moveTo(170, 340);
        path5.lineTo(230, 340);
        path5.lineTo(200, 290);
        path5.close();

        // 定义一个五角形
        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();

        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();

        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();

        shader = new LinearGradient(0, 0, 40, 60, new int[]{Color.RED, Color.GREEN,
                Color.BLUE, Color.YELLOW}, null, Shader.TileMode.REPEAT);
    }

    private void setPaintStyleStroke() {
        paint.setAntiAlias(true);
        paint.setColor(Color.BLUE);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(3);
    }

    private void setPaintStyleFill() { // 设置填充风格后绘制
        paint.setStyle(Paint.Style.FILL);
        paint.setColor(Color.RED);
    }

    private void setPaintShader() { // 设置渐变后绘制
        paint.setShader(shader);
        paint.setShadowLayer(45, 10, 10, Color.GRAY);
    }

    private void setPaintTextSize() {
        paint.setShader(null);
        paint.setTextSize(24);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        // 将整张画布绘制成白色
        canvas.drawColor(Color.WHITE);

        setPaintStyleStroke();
        // 绘制圆形
        canvas.drawCircle(40, 40, 30, paint);
        // 绘制正方形
        canvas.drawRect(10, 80, 70, 140, paint);
        // 绘制矩形
        canvas.drawRect(10, 150, 70, 190, paint);
        // 绘制圆角矩形
        canvas.drawRoundRect(rectF0, 15, 15, paint);
        // 绘制椭圆
        canvas.drawOval(rectF1, paint);
        canvas.drawPath(path1, paint);
        canvas.drawPath(path2, paint);

        setPaintStyleFill();
        // 绘制圆形
        canvas.drawCircle(120, 40, 30, paint);
        // 绘制正方形
        canvas.drawRect(90, 80, 150, 140, paint);
        // 绘制矩形
        canvas.drawRect(90, 150, 150, 190, paint);
        // 绘制圆角矩形
        canvas.drawRoundRect(rectF2, 15, 15, paint);
        // 绘制椭圆
        canvas.drawOval(rectF3, paint);
        canvas.drawPath(path3, paint);
        canvas.drawPath(path4, paint);


        setPaintShader();
        // 绘制圆形
        canvas.drawCircle(200, 40, 30, paint);
        // 绘制正方形
        canvas.drawRect(170, 80, 230, 140, paint);
        // 绘制矩形
        canvas.drawRect(170, 150, 230, 190, paint);
        // 绘制圆角矩形
        canvas.drawRoundRect(rectF4, 15, 15, paint);
        // 绘制椭圆
        canvas.drawOval(rectF5, paint);
        canvas.drawPath(path5, paint);
        canvas.drawPath(path6, paint);

        setPaintTextSize();
        canvas.drawText("Circle", 300, 50, paint);
        canvas.drawText("Square", 300, 120, paint);
        canvas.drawText("Rectangle", 300, 175, paint);
        canvas.drawText("Round Rectangle", 300, 220, paint);
        canvas.drawText("Oval", 300, 260, paint);
        canvas.drawText("Triangle", 300, 325, paint);
        canvas.drawText("Pentagon", 300, 390, paint);
    }
}

主布局文件的内容如下：

主程序文件的内容：

package com.toby.personal.testlistview;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    final private static String TAG = "Toby_Test";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

}

运行显示效果：

显示效果

参考文献：《疯狂Android讲义（第2版）》