TextView内マージンなし

NoPaddingTextView

package widget.textview;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.support.v7.widget.AppCompatTextView;
import android.util.AttributeSet;

import com.xalikai.bnmdteacherend.R;

/**
 * Created on 2019/3/14.
 *
 * @author    
 * @desc NoPaddingTextView
 */
public class NoPaddingTextView extends AppCompatTextView {
    private Paint paint = getPaint();
    private Rect rect = new Rect();
    /**
     *       （true  、false   ）
     */
    private Boolean toRemoveTheInBodyMargin = false;

    public NoPaddingTextView(Context context) {
        super(context);
    }

    public NoPaddingTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initAttributes(context, attrs);
    }

    public NoPaddingTextView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initAttributes(context, attrs);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (toRemoveTheInBodyMargin) {
            calculateTextParams();
            setMeasuredDimension(rect.right - rect.left, -rect.top + rect.bottom);
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        drawText(canvas);
    }

    /**
     *      
     *
     * @param context    
     * @param attrs     
     */
    private void initAttributes(Context context, AttributeSet attrs) {
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.NoPaddingTextView);
        toRemoveTheInBodyMargin = typedArray.getBoolean(R.styleable.NoPaddingTextView_removeDefaultPadding, false);
        typedArray.recycle();
    }

    /**
     *      
     */
    private String calculateTextParams() {
        String text = getText().toString();
        int textLength = text.length();
        paint.getTextBounds(text, 0, textLength, rect);
        if (textLength == 0) {
            rect.right = rect.left;
        }
        return text;
    }

    /**
     *    
     */
    private void drawText(Canvas canvas) {
        String text = calculateTextParams();
        int left = rect.left;
        int bottom = rect.bottom;
        rect.offset(-rect.left, -rect.top);
        paint.setAntiAlias(true);
        paint.setColor(getCurrentTextColor());
        canvas.drawText(text, (float) (-left), (float) (rect.bottom - bottom), paint);
    }
}

attrs