如何将文本放入drawable中？

Question

我正在尝试动态创建一个drawable用作自定义linearlayout的背景.它需要有哈希标记等(没什么大不了的),但也有标记哈希标记的数字(如标尺).我知道我可以创建文本元素并将它们放在linearlayout中,并且在drawable中只有哈希标记,但我希望它们也可以在drawable中使用,所以我不必进行两次测量计算.

Answer 1

下面是一个简单的示例,TextDrawable它的工作方式类似于普通的drawable,但允许您将text指定为唯一的构造函数变量:

public class TextDrawable extends Drawable {

    private final String text;
    private final Paint paint;

    public TextDrawable(String text) {

        this.text = text;

        this.paint = new Paint();
        paint.setColor(Color.WHITE);
        paint.setTextSize(22f);
        paint.setAntiAlias(true);
        paint.setFakeBoldText(true);
        paint.setShadowLayer(6f, 0, 0, Color.BLACK);
        paint.setStyle(Paint.Style.FILL);
        paint.setTextAlign(Paint.Align.LEFT);
    }

    @Override
    public void draw(Canvas canvas) {
        canvas.drawText(text, 0, 0, paint);
    }

    @Override
    public void setAlpha(int alpha) {
        paint.setAlpha(alpha);
    }

    @Override
    public void setColorFilter(ColorFilter cf) {
        paint.setColorFilter(cf);
    }

    @Override
    public int getOpacity() {
        return PixelFormat.TRANSLUCENT;
    }
}

Answer 2

我读过"专业Android 2应用程序开发"一书(由Reto Meier撰写).其中,它包含一个示例项目,您可以在其中创建一个简单的指南针应用程序,您可以在其中"绘制"文本,标记等

简要说明是您创建一个扩展android.view.View该类并覆盖该onDraw(Canvas)方法的类.

本书的所有源代码均可在此处下载:http://www.wrox.com/WileyCDA/WroxTitle/Professional-Android-2-Application-Development.productCd-0470565527,descCd-DOWNLOAD.html.如果您下载代码并查看名为"第4章指南针"的项目,我相信您会找到您要找的内容:)

Answer 3

看看Plowman的答案,并尝试根据我的需要调整它,我在这个链接中找到了一个用于Camera的类

这是TextDrawable类的代码.用Plowmans看起来很漂亮,但对我来说效果更好:

import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.Paint.Align;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.TypedValue;

public class TextDrawable extends Drawable {
    private static final int DEFAULT_COLOR = Color.WHITE;
    private static final int DEFAULT_TEXTSIZE = 15;
    private Paint mPaint;
    private CharSequence mText;
    private int mIntrinsicWidth;
    private int mIntrinsicHeight;

    public TextDrawable(Resources res, CharSequence text) {
        mText = text;
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setColor(DEFAULT_COLOR);
        mPaint.setTextAlign(Align.CENTER);
        float textSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,
                DEFAULT_TEXTSIZE, res.getDisplayMetrics());
        mPaint.setTextSize(textSize);
        mIntrinsicWidth = (int) (mPaint.measureText(mText, 0, mText.length()) + .5);
        mIntrinsicHeight = mPaint.getFontMetricsInt(null);
    }
    @Override
    public void draw(Canvas canvas) {
        Rect bounds = getBounds();
        canvas.drawText(mText, 0, mText.length(),
                bounds.centerX(), bounds.centerY(), mPaint);
    }
    @Override
    public int getOpacity() {
        return mPaint.getAlpha();
    }
    @Override
    public int getIntrinsicWidth() {
        return mIntrinsicWidth;
    }
    @Override
    public int getIntrinsicHeight() {
        return mIntrinsicHeight;
    }
    @Override
    public void setAlpha(int alpha) {
        mPaint.setAlpha(alpha);
    }
    @Override
    public void setColorFilter(ColorFilter filter) {
        mPaint.setColorFilter(filter);
    }
}

Answer 4

要回答上面关于如何使文本居中的评论：

mPaint.textAlign = Align.CENTER
...
// Centering for mixed case letters
canvas.drawText(mText, 0, mText.length,
        bounds.centerX().toFloat(), bounds.centerY().toFloat() - ((mPaint.descent() + mPaint.ascent()) / 2), mPaint)

// Centering for all uppercase letters
canvas.drawText(mText, 0, mText.length,
            bounds.centerX().toFloat(), bounds.centerY().toFloat() - mPaint.ascent() / 2, mPaint)