自定义控件 View生成小球可以拖动

最新推荐文章于 2020-05-25 00:46:31 发布

LI_YUANQI

最新推荐文章于 2020-05-25 00:46:31 发布

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本文链接：https://blog.youkuaiyun.com/LI_YUANQI/article/details/83720320

本文介绍了一个自定义的Android视图组件——圆形视图，该组件能够响应触摸事件并改变颜色，同时提供了动态绘制圆的功能。文章详细解析了如何使用Canvas、Paint等API进行图形绘制，以及如何通过MotionEvent实现触摸交互。

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import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Build;
import android.support.annotation.Nullable;
import android.support.annotation.RequiresApi;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class Yuan extends View{
int x=0;
int y=0;
Paint mPaint;
Boolean weizhi;

public Yuan(Context context) {
    super(context);
}

public Yuan(Context context, @Nullable AttributeSet attrs) {
    super(context, attrs);
    mPaint=new Paint();
    mPaint.setColor(Color.RED);
    mPaint.setAlpha(200);
    mPaint.setStrokeWidth(8);
    mPaint.setAntiAlias(true);

}

public Yuan(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    x = this.getWidth()/2;
    y = this.getHeight()/2;
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
   canvas.drawCircle(x,y,50,mPaint);


}

@Override
public boolean onTouchEvent(MotionEvent event) {
    switch (event.getAction()){
        case MotionEvent.ACTION_DOWN:
            mPaint.setColor(Color.BLUE);
            int dx = (int) event.getX();
            int dy = (int) event.getY();
             weizhi = weizhi(dx, dy);
            break;
        case MotionEvent.ACTION_MOVE:

            int mx = (int) event.getX();
            int my = (int) event.getY();
            if (weizhi){
                x=mx;
                y=my;
                invalidate();
            }
            break;
        case MotionEvent.ACTION_UP:
            mPaint.setColor(Color.BLUE);
            break;
    }
   return true;

}

private Boolean weizhi(int dx, int dy) {
    double sqrt = Math.sqrt((dx - x) * (dx - x) + (dy - y) * (dy - y));
    if (sqrt<=50){
        return true;
    }
    return false;
}

}

<liyuanqi.bwie.com.zidingyikj01.Yuan
android:layout_width=“wrap_content”
android:layout_height=“wrap_content” />