如何绘制嵌套循环编程 [英] how to draw nested circle programmatically

问题描述

在这里，我使用的图层列表中通过使用XML抽签嵌套环

Here I am using layer list to draw nested Circle by using XML

<item>
    <shape android:shape="oval" >
        <stroke
            android:width="1dp"
            android:color="@android:color/holo_orange_light" />

        <padding
            android:bottom="7dp"
            android:left="7dp"
            android:right="7dp"
            android:top="7dp" />
    </shape>
</item>
<item>
    <shape android:shape="oval" >
        <solid android:color="@color/welcome_bg" />
    </shape>
</item>

不，我想同样的嵌套循环使用编程方式，因为我想动态改变颜色或有什么办法在上面

No I want same nested circle by using programmatically because I want to change color dynamically or is there any way to change color dynamically in xml provided above

下面是我的自定义视图

public class MyView extends EditText {

public MyView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);

}

public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);

}

public MyView(Context context) {
    super(context);

}

@Override
protected void onDraw(Canvas canvas) {
    Paint paint = new Paint();
    paint.setStyle(Paint.Style.STROKE);
    paint.setColor(Color.GRAY);

    RectF oval1 = new RectF(50, 50, 300, 300);
    canvas.drawOval(oval1, paint);

    paint.setStyle(Paint.Style.FILL);
    paint.setColor(Color.RED);
    RectF oval2 = new RectF(55, 55, 295, 295);
    canvas.drawOval(oval2, paint);

}
}

感谢

推荐答案

在使用XML，规定的尺寸是DP - 密度无关的像素。但是，在你的code绘图功能，采取实际像素作为参数，你必须考虑到这一点，并计算出自己正确的价值观。

When you use xml, specified dimensions are in dp - density independent pixels. But in your code drawing functions take actual pixels as parameters and you have to take that into account and calculate proper values yourself.

根据设备屏幕申报密度1DP将被转换为：

Depending on your device declared screen density 1dp will be translated to:

• LDPI（120 DPI） - 0.75 PIX


• MDPI（160 DPI） - 1 PIX


• 华电国际（240 DPI） - 1.5 PIX


• xhdpi（320 DPI） - 2 PIX


• xxhdpi（480 DPI） - 3 PIX


• xxxhdpi（640 DPI） - 4 PIX

公式计算实际像素为 PX = DP *（DPI / 160）

public class MyView extends EditText {

float mDensityScale;    

public MyView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init(context, attrs, defStyleAttr);
}

public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context, attrs, 0);    
}

public MyView(Context context) {
    super(context);
    init(context, null, 0);
}

private void init(Context context, AttributeSet attrs, int defStyle)
{
    final DisplayMetrics dm = context.getResources().getDisplayMetrics();
    mDensityScale = dm.density;
}

private float pix(float dp)
{
    return dp * mDensityScale;
}   

@Override
protected void onDraw(Canvas canvas) {
    Paint paint = new Paint();
    paint.setStyle(Paint.Style.STROKE);
    paint.setColor(Color.GRAY);

    RectF oval1 = new RectF(pix(50), pix(50), pix(300), pix(300));
    canvas.drawOval(oval1, paint);

    paint.setStyle(Paint.Style.FILL);
    paint.setColor(Color.RED);
    RectF oval2 = new RectF(pix(55), pix(55), pix(295), pix(295));
    canvas.drawOval(oval2, paint);

}
}

您可以阅读更多：

• 支持多种屏幕


• Difference PX之间，DP，倾角和SP在Android的？

• Supporting Multiple Screens
• Difference between px, dp, dip and sp in Android?

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