我正在尝试动态创建可绘制对象,以用作自定义线性布局的背景。它需要有刻度线等内容(没问题),还需要标记刻度线的数字(就像标尺一样)。我知道我可以创建文本元素并将其放置在线性布局内,并且只在可绘制对象中放置刻度线,但我希望它们也在可绘制对象内,这样我不必进行两次测量计算。
这是一个简短的示例,展示了如何使用TextDrawable
,它像普通的drawable一样工作,但允许你将文本作为唯一的构造函数变量进行指定:
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;
}
}
paint.setTextAlign(Paint.Align.CENTER);
。 - plowmanandroid.view.View
类并重写onDraw(Canvas)
方法的类。看了Plowman的答案并试图根据我的需求进行调整,我发现一个用于此链接中相机的类。
这是TextDrawable类的代码。它看起来与Plowman的代码非常相似,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);
}
}
回答上面有关如何居中文本的评论:
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)
这样可以让您将任何视图放入Drawable中,包括TextView。您甚至可以在XML布局中使用样式。
public class ViewDrawable extends Drawable {
final View mView;
public ViewDrawable(final Context context, final @LayoutRes int layoutId) {
this(LayoutInflater.from(context).inflate(layoutId, null));
}
public ViewDrawable(final @NonNull View view) {
mView = view;
}
public View getView() {
return mView;
}
@Override
public void setBounds(int left, int top, int right, int bottom) {
super.setBounds(left, top, right, bottom);
final int widthMeasureSpec = View.MeasureSpec.makeMeasureSpec(right - left, View.MeasureSpec.EXACTLY);
final int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(bottom - top, View.MeasureSpec.EXACTLY);
mView.measure(widthMeasureSpec, heightMeasureSpec);
mView.layout(left, top, right, bottom);
}
@Override
public void draw(@NonNull Canvas canvas) {
mView.draw(canvas);
}
@Override
public void setAlpha(int alpha) {
mView.setAlpha(alpha/255f);
}
@Override
public void setColorFilter(@Nullable ColorFilter colorFilter) {
}
@Override
public int getOpacity() {
return PixelFormat.UNKNOWN;
}
}