安卓:drawable

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="ring" >

    <size
        android:height="50dp"
        android:width="300dp" />
    <!-- 拐角的弧度 -->
    <corners android:radius="10dp" />
    <!-- 背景 -->
    <!-- <solid android:color="#ff0000" /> -->

    <!-- 渐变,和背景色冲突 -->
    <gradient
        android:angle="270"
        android:centerColor="#00ff00"
        android:endColor="#0000ff"
        android:startColor="#ff0000" />
    <!-- stroke:击球,轻抚 -> 边框 -->
    <stroke
        android:width="5dp"
        android:color="#00ffff" />

</shape>

        setContentView(R.layout.activity_main);
        // 获取像素密度
        float scales = getResources().getDisplayMetrics().density;
        ZrLog.log(scales +"");
        // 像素 = 独立像素*像素密度+0.5
        double width = scales * 10 +  0.5;

        Button bt = (Button) findViewById(R.id.bt);

        Drawable d = getResources().getDrawable(R.drawable.testdrawable);
        // 获取drawable尺寸
        d.setBounds(0, 0, d.getIntrinsicHeight(), d.getIntrinsicHeight());
        bt.setBackground(d);

        // 生成位图
        Bitmap bm = BitmapFactory.decodeResource(getResources(),
                R.drawable.testdrawable);