Android:如何检测画布绘制的线条中的某个点?

时间:2016-04-15 03:36:48

标签: android android-canvas

使用与背景颜色不同的颜色绘制线条。然后将位图放在画布中的数组中。如果数组中给定点的颜色与线条的颜色相同,则该点在该线条中。另外,我不想在我的应用程序中显示画布。

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private Button btnCheck;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btnCheck = (Button) findViewById(R.id.btn_check);
        btnCheck.setOnClickListener(click);
    }

    private View.OnClickListener click = new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            int width = 60, height =60;
            int startX = 15, startY = 8;
            int stopX  = 15, stopY  = 20;

            Paint paint = new Paint();
            paint.setStrokeWidth(5);
            paint.setColor(Color.RED);

            Bitmap baseBitmap;
            Canvas canvas;

            baseBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
            canvas = new Canvas(baseBitmap);
            canvas.drawColor(Color.WHITE);

            canvas.drawLine(startX, startY, stopX, stopY, paint);

            int[] arrImage = new int[width*height];
            baseBitmap.setPixels(arrImage, 0, width, 0, 0, width, height);

            int[][] points = new int[][]{
                    {15, 8},{15, 10},
                    {30, 30},{40, 40}};

            String result = "";
            for (int i=0; i<points.length; ++i) {
                int index = getPixelIndex(width, points[i][0], points[i][1]);
                result = result + ":" + (arrImage[index] == Color.RED);
            }
            Toast.makeText(MainActivity.this, result, Toast.LENGTH_LONG).show();

        }
    };

    public int getPixelIndex(int imageWidth, int pos_x, int pos_y) {
        return pos_y * imageWidth + pos_x;
    }

}

但是四个结果都是false,这不是我预期的结果。  我的代码有什么错误?

1 个答案:

答案 0 :(得分:0)

你的问题就在这一行:

baseBitmap.setPixels(arrImage, 0, width, 0, 0, width, height);

setPixels()方法用传递的数组替换Bitmap中的像素数据,在这种情况下,该数组全为零。它不会更改数组的值,因此在进行比较时它们仍将全为零。

您需要getPixels()方法。