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這篇文章給大家介紹怎么在android中將px和dp進(jìn)行轉(zhuǎn)換,內(nèi)容非常詳細(xì),感興趣的小伙伴們可以參考借鑒,希望對(duì)大家能有所幫助。
在Android開(kāi)發(fā)中dp和px,sp和px之間的轉(zhuǎn)換時(shí)必不可少的,網(wǎng)上流傳的方法
public class DisplayUtils { /** * convert px to its equivalent dp * 將px轉(zhuǎn)換為與之相等的dp */ public static int px2dp(Context context, float pxValue) { final float scale = context.getResources().getDisplayMetrics().density; return (int) (pxValue / scale + 0.5f); } /** * convert dp to its equivalent px * 將dp轉(zhuǎn)換為與之相等的px */ public static int dp2px(Context context, float dipValue) { final float scale = context.getResources().getDisplayMetrics().density; return (int) (dipValue * scale + 0.5f); } /** * convert px to its equivalent sp * 將px轉(zhuǎn)換為sp */ public static int px2sp(Context context, float pxValue) { final float fontScale = context.getResources().getDisplayMetrics().scaledDensity; return (int) (pxValue / fontScale + 0.5f); } /** * convert sp to its equivalent px * 將sp轉(zhuǎn)換為px */ public static int sp2px(Context context, float spValue) { final float fontScale = context.getResources().getDisplayMetrics().scaledDensity; return (int) (spValue * fontScale + 0.5f); } }
關(guān)于轉(zhuǎn)換公式中,通過(guò)類比一元一次函數(shù),怎么看都是有問(wèn)題的,這么明顯的問(wèn)題,為什么沒(méi)人糾正,后來(lái)發(fā)現(xiàn)是自己并沒(méi)有理解,原因是float類型在強(qiáng)轉(zhuǎn)為int類型是,用的是去尾法,精度上有較大差異,所以通過(guò)+0.5f的方式,將去尾法轉(zhuǎn)變成四舍五入法,提高精度。
調(diào)用TypedValue類實(shí)現(xiàn)轉(zhuǎn)換
/** * convert dp to its equivalent px */ protected int dp2px(int dp){ return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp,getResources().getDisplayMetrics()); } /** * convert sp to its equivalent px */ protected int sp2px(int sp){ return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, sp,getResources().getDisplayMetrics()); } public class TypedValue { ... /** {@link #TYPE_DIMENSION} complex unit: Value is raw pixels. */ public static final int COMPLEX_UNIT_PX = 0; /** {@link #TYPE_DIMENSION} complex unit: Value is Device Independent * Pixels. */ public static final int COMPLEX_UNIT_DIP = 1; /** {@link #TYPE_DIMENSION} complex unit: Value is a scaled pixel. */ public static final int COMPLEX_UNIT_SP = 2; /** {@link #TYPE_DIMENSION} complex unit: Value is in points. */ public static final int COMPLEX_UNIT_PT = 3; /** {@link #TYPE_DIMENSION} complex unit: Value is in inches. */ public static final int COMPLEX_UNIT_IN = 4; /** {@link #TYPE_DIMENSION} complex unit: Value is in millimeters. */ public static final int COMPLEX_UNIT_MM = 5; /** * Converts an unpacked complex data value holding a dimension to its final floating * point value. The two parameters <var>unit</var> and <var>value</var> * are as in {@link #TYPE_DIMENSION}. * * @param unit The unit to convert from. * @param value The value to apply the unit to. * @param metrics Current display metrics to use in the conversion -- * supplies display density and scaling information. * * @return The complex floating point value multiplied by the appropriate * metrics depending on its unit. */ public static float applyDimension(int unit, float value, DisplayMetrics metrics) { switch (unit) { case COMPLEX_UNIT_PX: return value; case COMPLEX_UNIT_DIP: return value * metrics.density; case COMPLEX_UNIT_SP: return value * metrics.scaledDensity; case COMPLEX_UNIT_PT: return value * metrics.xdpi * (1.0f/72); case COMPLEX_UNIT_IN: return value * metrics.xdpi; case COMPLEX_UNIT_MM: return value * metrics.xdpi * (1.0f/25.4f); } return 0; } ... }
Android是一種基于Linux內(nèi)核的自由及開(kāi)放源代碼的操作系統(tǒng),主要使用于移動(dòng)設(shè)備,如智能手機(jī)和平板電腦,由美國(guó)Google公司和開(kāi)放手機(jī)聯(lián)盟領(lǐng)導(dǎo)及開(kāi)發(fā)。
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