Android图文居中显示控件使用方法详解

最近项目中用到了文字图标的按钮，需要居中显示，如果用TextView实现的方式，必须同时设置padding和drawablePadding。如下：

<androidx.appcompat.widget.AppCompatTextView
  android:layout_width="200dp"
  android:layout_height="wrap_content"
  android:drawableLeft="@drawable/ic_xxx"
  android:drawablePadding="-60dp"
  android:minHeight="48dp"
  android:gravity="center"
  android:padding="80dp" />

这种方式需要自己做精确计算。比较麻烦。另外还有一种方式就是用线性布局包裹ImageView和TextView，但这样会增加布局层级。于是自己封装了一个控件DrawableCenterTextView。

attrs.xml文件中定义属性：

<declare-styleable name="DrawableCenterTextView">
  <attr name="android:text" />
  <attr name="android:textColor" />
  <attr name="android:textSize" />
  <attr name="android:textStyle" />
  <attr name="android:drawablePadding" />
  <attr name="android:drawableLeft" />
  <attr name="android:drawableTop" />
  <attr name="android:drawableRight" />
  <attr name="android:drawableBottom" />
</declare-styleable>

对应的Java代码如下：

public class DrawableCenterTextView extends View {
static final int LEFT = 0;
static final int TOP = 1;
static final int RIGHT = 2;
static final int BOTTOM = 3;
private CharSequence mText;
private ColorStateList mTextColor;
private float mTextSize;
private int mTextStyle;
private int mDrawablePadding;
private Drawable[] mCompoundDrawables;
private Rect mTextBounds;
private Rect mDrawableLeftBounds;
private Rect mDrawableTopBounds;
private Rect mDrawableRightBounds;
private Rect mDrawableBottomBounds;
private TextPaint mTextPaint;
public DrawableCenterTextView(Context context) {
this(context, null);
}
public DrawableCenterTextView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public DrawableCenterTextView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
Drawable drawableLeft = null, drawableTop = null, drawableRight = null, drawableBottom = null;
TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.DrawableCenterTextView, defStyleAttr, 0);
mText = ta.getText(R.styleable.DrawableCenterTextView_android_text);
mTextColor = ta.getColorStateList(R.styleable.DrawableCenterTextView_android_textColor);
mTextSize = ta.getDimensionPixelSize(R.styleable.DrawableCenterTextView_android_textSize, 15);
mTextStyle = ta.getInt(R.styleable.DrawableCenterTextView_android_textStyle, 0);
drawableLeft = ta.getDrawable(R.styleable.DrawableCenterTextView_android_drawableLeft);
drawableTop = ta.getDrawable(R.styleable.DrawableCenterTextView_android_drawableTop);
drawableRight = ta.getDrawable(R.styleable.DrawableCenterTextView_android_drawableRight);
drawableBottom = ta.getDrawable(R.styleable.DrawableCenterTextView_android_drawableBottom);
mDrawablePadding = ta.getDimensionPixelSize(R.styleable.DrawableCenterTextView_android_drawablePadding, 0);
ta.recycle();
if (mTextColor == null) {
mTextColor = ColorStateList.valueOf(0xFF000000);
}
mTextPaint = new TextPaint(Paint.ANTI_ALIAS_FLAG);
mTextPaint.density = getResources().getDisplayMetrics().density;
mTextPaint.setTextSize(mTextSize);
setTypeface(Typeface.create(Typeface.DEFAULT, mTextStyle));
setCompoundDrawablesWithIntrinsicBounds(drawableLeft, drawableTop, drawableRight, drawableBottom);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
int widthSize = MeasureSpec.getSize(widthMeasureSpec);
int heightSize = MeasureSpec.getSize(heightMeasureSpec);
int width;
int height;
//计算文本范围
calcTextBounds();
if (widthMode == MeasureSpec.EXACTLY) {
width = widthSize;
} else {
width = mTextBounds.width();
if (mCompoundDrawables != null) {
if (mCompoundDrawables[TOP] != null) {
width = Math.max(width, mDrawableTopBounds.width());
}
if (mCompoundDrawables[BOTTOM] != null) {
width = Math.max(width, mDrawableBottomBounds.width());
}
//加上左右内边距及drawable宽度和drawable间距
width += getCompoundPaddingLeft() + getCompoundPaddingRight();
width = Math.max(width, getSuggestedMinimumWidth());
if (widthMode == MeasureSpec.AT_MOST) {
width = Math.min(widthSize, width);
}
}
}
if (heightMode == MeasureSpec.EXACTLY) {
height = heightSize;
} else {
height = mTextBounds.height();
if (mCompoundDrawables != null) {
if (mCompoundDrawables[LEFT] != null) {
height = Math.max(height, mDrawableLeftBounds.height());
}
if (mCompoundDrawables[RIGHT] != null) {
height = Math.max(height, mDrawableRightBounds.height());
}
//加上上下内边距及drawable高度和drawable间距
height += getCompoundPaddingTop() + getCompoundPaddingBottom();
height = Math.max(height, getSuggestedMinimumHeight());
if (heightMode == MeasureSpec.AT_MOST) {
height = Math.min(heightSize, height);
}
}
}
setMeasuredDimension(width, height);
}
public int getCompoundPaddingTop() {
if (mCompoundDrawables == null || mCompoundDrawables[TOP] == null) {
return getPaddingTop();
} else {
Rect rect = new Rect();
mCompoundDrawables[TOP].copyBounds(rect);
return getPaddingTop() + mDrawablePadding + rect.height();
}
}
public int getCompoundPaddingBottom() {
if (mCompoundDrawables == null || mCompoundDrawables[BOTTOM] == null) {
return getPaddingBottom();
} else {
Rect rect = new Rect();
mCompoundDrawables[BOTTOM].copyBounds(rect);
return getPaddingBottom() + mDrawablePadding + rect.height();
}
}
public int getCompoundPaddingLeft() {
if (mCompoundDrawables == null || mCompoundDrawables[LEFT] == null) {
return getPaddingLeft();
} else {
Rect rect = new Rect();
mCompoundDrawables[LEFT].copyBounds(rect);
return getPaddingLeft() + mDrawablePadding + rect.width();
}
}
public int getCompoundPaddingRight() {
if (mCompoundDrawables == null || mCompoundDrawables[RIGHT] == null) {
return getPaddingRight();
} else {
Rect rect = new Rect();
mCompoundDrawables[RIGHT].copyBounds(rect);
return getPaddingRight() + mDrawablePadding + rect.width();
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
int vspace = getBottom() - getTop() - getCompoundPaddingBottom() - getCompoundPaddingTop(); //剩余垂直可绘制文本空间大小
int hspace = getRight() - getLeft() - getCompoundPaddingRight() - getCompoundPaddingLeft(); //剩余水平可绘制文本空间大小
if (mCompoundDrawables != null) {
if (mCompoundDrawables[LEFT] != null) {
canvas.save();
canvas.translate((hspace - mTextBounds.width()) / 2.0f + getPaddingLeft(),
getCompoundPaddingTop() + (vspace - mDrawableLeftBounds.height()) / 2.0f);
mCompoundDrawables[LEFT].draw(canvas);
canvas.restore();
}
if (mCompoundDrawables[RIGHT] != null) {
canvas.save();
canvas.translate(getRight() - getLeft() - getPaddingRight() - (hspace - mTextBounds.width()) / 2.0f - mDrawableRightBounds.width(),
getCompoundPaddingTop() + (vspace - mDrawableRightBounds.height()) / 2.0f);
mCompoundDrawables[RIGHT].draw(canvas);
canvas.restore();
}
if (mCompoundDrawables[TOP] != null) {
canvas.save();
canvas.translate(getCompoundPaddingLeft()
+ (hspace - mDrawableTopBounds.width()) / 2.0f, (vspace - mTextBounds.height()) / 2.0f + getPaddingTop());
mCompoundDrawables[TOP].draw(canvas);
canvas.restore();
}
if (mCompoundDrawables[BOTTOM] != null) {
canvas.save();
canvas.translate(getCompoundPaddingLeft()
+ (hspace - mDrawableBottomBounds.width()) / 2.0f,
getBottom() - getTop() - getPaddingBottom() - (vspace - mTextBounds.height()) / 2.0f - mDrawableBottomBounds.height());
mCompoundDrawables[BOTTOM].draw(canvas);
canvas.restore();
}
}
if (!TextUtils.isEmpty(mText)) {
float startX = (hspace - mTextBounds.width()) / 2.0f + getCompoundPaddingLeft();
//因为drawText以baseline为基准，因此需要向下移ascent
float startY = (vspace - mTextBounds.height()) / 2.0f + getCompoundPaddingTop() - mTextPaint.getFontMetrics().ascent;
mTextPaint.setColor(mTextColor.getColorForState(getDrawableState(), 0));
canvas.drawText(mText, 0, mText.length(), startX, startY, mTextPaint);
}
}
@Override
protected void drawableStateChanged() {
super.drawableStateChanged();
if (mTextColor != null && mTextColor.isStateful()) {
mTextPaint.setColor(mTextColor.getColorForState(getDrawableState(), 0));
}
if (mCompoundDrawables != null) {
final int[] state = getDrawableState();
for (Drawable dr : mCompoundDrawables) {
if (dr != null && dr.isStateful() && dr.setState(state)) {
invalidateDrawable(dr);
}
}
}
}
public void setCompoundDrawablesWithIntrinsicBounds(@Nullable Drawable left,
@Nullable Drawable top, @Nullable Drawable right, @Nullable Drawable bottom) {
if (left != null) {
left.setBounds(0, 0, left.getIntrinsicWidth(), left.getIntrinsicHeight());
}
if (right != null) {
right.setBounds(0, 0, right.getIntrinsicWidth(), right.getIntrinsicHeight());
}
if (top != null) {
top.setBounds(0, 0, top.getIntrinsicWidth(), top.getIntrinsicHeight());
}
if (bottom != null) {
bottom.setBounds(0, 0, bottom.getIntrinsicWidth(), bottom.getIntrinsicHeight());
}
setCompoundDrawables(left, top, right, bottom);
}
public void setCompoundDrawables(@Nullable Drawable left, @Nullable Drawable top,
@Nullable Drawable right, @Nullable Drawable bottom) {
if (mCompoundDrawables == null) {
mCompoundDrawables = new Drawable[4];
} else {
if (mCompoundDrawables[LEFT] != null && mCompoundDrawables[LEFT] != left) {
mCompoundDrawables[LEFT].setCallback(null);
}
if (mCompoundDrawables[TOP] != null && mCompoundDrawables[TOP] != top) {
mCompoundDrawables[TOP].setCallback(null);
}
if (mCompoundDrawables[RIGHT] != null && mCompoundDrawables[RIGHT] != right) {
mCompoundDrawables[RIGHT].setCallback(null);
}
if (mCompoundDrawables[BOTTOM] != null && mCompoundDrawables[BOTTOM] != bottom) {
mCompoundDrawables[BOTTOM].setCallback(null);
}
}
if (left != null) {
mDrawableLeftBounds = new Rect();
left.copyBounds(mDrawableLeftBounds);
left.setCallback(this);
mCompoundDrawables[LEFT] = left;
} else {
mCompoundDrawables[LEFT] = null;
}
if (top != null) {
mDrawableTopBounds = new Rect();
top.copyBounds(mDrawableTopBounds);
top.setCallback(this);
mCompoundDrawables[TOP] = top;
} else {
mCompoundDrawables[TOP] = null;
}
if (right != null) {
mDrawableRightBounds = new Rect();
right.copyBounds(mDrawableRightBounds);
right.setCallback(this);
mCompoundDrawables[RIGHT] = right;
} else {
mCompoundDrawables[RIGHT] = null;
}
if (bottom != null) {
mDrawableBottomBounds = new Rect();
bottom.copyBounds(mDrawableBottomBounds);
bottom.setCallback(this);
mCompoundDrawables[BOTTOM] = bottom;
} else {
mCompoundDrawables[BOTTOM] = null;
}
invalidate();
requestLayout();
}
public void setText(CharSequence text) {
this.mText = text;
invalidate();
requestLayout();
}
public void setTextSize(float textSize) {
this.mTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, textSize, getResources().getDisplayMetrics());
invalidate();
requestLayout();
}
public void setTextColor(@ColorInt int textColor) {
this.mTextColor = ColorStateList.valueOf(textColor);
invalidate();
}
public void setTypeface(@Nullable Typeface tf) {
if (mTextPaint.getTypeface() != tf) {
mTextPaint.setTypeface(tf);
requestLayout();
invalidate();
}
}
private void calcTextBounds() {
mTextBounds = new Rect();
if (TextUtils.isEmpty(mText)) return;
if (Build.VERSION.SDK_INT > Build.VERSION_CODES.Q) {
mTextPaint.getTextBounds(mText, 0, mText.length(), mTextBounds);
} else {
int width = (int) Math.ceil(mTextPaint.measureText(mText.toString()));
Paint.FontMetrics fontMetrics = mTextPaint.getFontMetrics();
int height = (int) Math.ceil(fontMetrics.descent - fontMetrics.ascent);
mTextBounds.set(0, 0, width, height);
}
}
}

感谢大家的支持，如有错误请指正。

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