在我们平时做项目的时候，经常会遇到一些需要显示图片的地方，这些图片默认的占位图，怎么显示才比较合理呢，比如头像，默认图片 可以是名字生成的图片这样比千篇一律的默认图，显示效果更佳。下边是效果图：
直接上代码：先说用法
/** * 根据文字生成drawable * @param name 显示在图片的名字 * @param fontRes 字体大小 * @param width 图片的宽度 * @param height 图片的高度 * @return */
public static TextDrawable getDefaultDrawable(String name, int fontRes, int width, int height) { String username = name; if ((name != null && name.length() >= 2)) { username = name.substring(name.length() - 2, name.length()); } else if (BackwardSupportUtil.isNullOrNil(name)) { username = ""; } return TextDrawable.builder() .beginConfig() .fontSize(fontRes) .width(width) .height(height) .endConfig() .buildRound(username, getColorBySeed(BackwardSupportUtil.nullAsNil(username)));}
说明：主要看一下下边代码的思路，学习东西要先学会它的主要实现思路，理解原理。首先它是继承了ShapeDrawable ，通过build方法构造出自己想要的图片的属性，然后再用paint绘制出图形。下边是主要代码
public class TextDrawable extends ShapeDrawable { private final Paint textPaint; private final Paint borderPaint; private static final float SHADE_FACTOR = 0.9f; private final String text; private final int color; private final RectShape shape; private final int height; private final int width; private final int fontSize; private final float radius; private final int borderThickness; private TextDrawable(Builder builder) { super(builder.shape); // shape properties shape = builder.shape; height = builder.height; width = builder.width; radius = builder.radius; // text and color text = builder.toUpperCase ? builder.text.toUpperCase() : builder.text; color = builder.color; // text paint settings fontSize = builder.fontSize; textPaint = new Paint(); textPaint.setColor(builder.textColor); textPaint.setAntiAlias(true); textPaint.setFakeBoldText(builder.isBold); textPaint.setStyle(Paint.Style.FILL); textPaint.setTypeface(builder.font); textPaint.setTextAlign(Paint.Align.CENTER); textPaint.setStrokeWidth(builder.borderThickness); // border paint settings borderThickness = builder.borderThickness; borderPaint = new Paint(); borderPaint.setColor(getDarkerShade(color)); borderPaint.setStyle(Paint.Style.STROKE); borderPaint.setStrokeWidth(borderThickness); // drawable paint color Paint paint = getPaint(); paint.setColor(color); } private int getDarkerShade(int color) { return Color.rgb((int)(SHADE_FACTOR * Color.red(color)), (int)(SHADE_FACTOR * Color.green(color)), (int)(SHADE_FACTOR * Color.blue(color))); } @Override public void draw(Canvas canvas) { super.draw(canvas); Rect r = getBounds(); // draw border if (borderThickness > 0) { drawBorder(canvas); } int count = canvas.save(); canvas.translate(r.left, r.top); // draw text int width = this.width < 0 ? r.width() : this.width; int height = this.height < 0 ? r.height() : this.height; int fontSize = this.fontSize < 0 ? (Math.min(width, height) / 2) : this.fontSize; textPaint.setTextSize(fontSize); canvas.drawText(text, width / 2, height / 2 - ((textPaint.descent() + textPaint.ascent()) / 2), textPaint); canvas.restoreToCount(count); } private void drawBorder(Canvas canvas) { RectF rect = new RectF(getBounds()); rect.inset(borderThickness/2, borderThickness/2); if (shape instanceof OvalShape) { canvas.drawOval(rect, borderPaint); } else if (shape instanceof RoundRectShape) { canvas.drawRoundRect(rect, radius, radius, borderPaint); } else { canvas.drawRect(rect, borderPaint); } } @Override public void setAlpha(int alpha) { textPaint.setAlpha(alpha); } @Override public void setColorFilter(ColorFilter cf) { textPaint.setColorFilter(cf); } @Override public int getOpacity() { return PixelFormat.TRANSLUCENT; } @Override public int getIntrinsicWidth() { return width; } @Override public int getIntrinsicHeight() { return height; } public static IShapeBuilder builder() { return new Builder(); } public static class Builder implements IConfigBuilder, IShapeBuilder, IBuilder { private String text; private int color; private int borderThickness; private int width; private int height; private Typeface font; private RectShape shape; public int textColor; private int fontSize; private boolean isBold; private boolean toUpperCase; public float radius; private Builder() { text = ""; color = Color.GRAY; textColor = Color.WHITE; borderThickness = 0; width = -1; height = -1; shape = new RectShape(); font = Typeface.create("sans-serif-light", Typeface.NORMAL); fontSize = -1; isBold = false; toUpperCase = false; } public IConfigBuilder width(int width) { this.width = width; return this; } public IConfigBuilder height(int height) { this.height = height; return this; } public IConfigBuilder textColor(int color) { this.textColor = color; return this; } public IConfigBuilder withBorder(int thickness) { this.borderThickness = thickness; return this; } public IConfigBuilder useFont(Typeface font) { this.font = font; return this; } public IConfigBuilder fontSize(int size) { this.fontSize = size; return this; } public IConfigBuilder bold() { this.isBold = true; return this; } public IConfigBuilder toUpperCase() { this.toUpperCase = true; return this; } @Override public IConfigBuilder beginConfig() { return this; } @Override public IShapeBuilder endConfig() { return this; } @Override public IBuilder rect() { this.shape = new RectShape(); return this; } @Override public IBuilder round() { this.shape = new OvalShape(); return this; } @Override public IBuilder roundRect(int radius) { this.radius = radius; float[] radii = {radius, radius, radius, radius, radius, radius, radius, radius}; this.shape = new RoundRectShape(radii, null, null); return this; } @Override public TextDrawable buildRect(String text, int color) { rect(); return build(text, color); } @Override public TextDrawable buildRoundRect(String text, int color, int radius) { roundRect(radius); return build(text, color); } @Override public TextDrawable buildRound(String text, int color) { round(); return build(text, color); } @Override public TextDrawable build(String text, int color) { this.color = color; this.text = text; return new TextDrawable(this); } } public interface IConfigBuilder { IConfigBuilder width(int width); IConfigBuilder height(int height); IConfigBuilder textColor(int color); IConfigBuilder withBorder(int thickness); IConfigBuilder useFont(Typeface font); IConfigBuilder fontSize(int size); IConfigBuilder bold(); IConfigBuilder toUpperCase(); IShapeBuilder endConfig(); } public interface IBuilder { TextDrawable build(String text, int color); } public interface IShapeBuilder { IConfigBuilder beginConfig(); IBuilder rect(); IBuilder round(); IBuilder roundRect(int radius); TextDrawable buildRect(String text, int color); TextDrawable buildRoundRect(String text, int color, int radius); TextDrawable buildRound(String text, int color); }}
