笔记11 | 动态设置TextView的字体大小

public class CustomTextView extends TextView {

    private static float DEFAULT_MIN_TEXT_SIZE = 1; 
    private static float DEFAULT_MAX_TEXT_SIZE = 48;

    // Attributes
    private Paint testPaint; 
    private float minTextSize, TextSize, maxTextSize;

    public CustomTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initialise();
    }

    private void initialise() {
        /*
         * limited size
         */
        testPaint = new Paint();
        testPaint.set(this.getPaint());
        TextSize = this.getTextSize();
        if (TextSize <= DEFAULT_MIN_TEXT_SIZE) {
            TextSize = DEFAULT_MIN_TEXT_SIZE;
        }
        if (TextSize >= DEFAULT_MAX_TEXT_SIZE) {
            TextSize = DEFAULT_MAX_TEXT_SIZE;
        }
        minTextSize = DEFAULT_MIN_TEXT_SIZE;
        maxTextSize = DEFAULT_MAX_TEXT_SIZE;
    };

    /*
     * (non-Javadoc)
     * @see android.widget.TextView#onTextChanged(java.lang.CharSequence, int, int, int)
     */
    @Override
    protected void onTextChanged(CharSequence text, int start, int before,
            int after) {
        super.onTextChanged(text, start, before, after);
        refitText(text.toString(), this.getWidth());
    }

    /*
     * (non-Javadoc)
     * @see android.view.View#onSizeChanged(int, int, int, int)
     */
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        if (w != oldw) {
            refitText(this.getText().toString(), w);
        }
    }
    //修改text方法
    private void refitText(String text, int textWidth) {

        if (textWidth > 0) {
            int availableWidth = textWidth - this.getPaddingLeft()
                    - this.getPaddingRight();// 获取实际TextView的画布可用大小        
            float trySize = TextSize; 
            float scaled = getContext().getResources().getDisplayMetrics().scaledDensity*trySize; //dp转为px后的textsize
            testPaint.setTextSize(scaled);
            while ((trySize > minTextSize||trySize<maxTextSize)&& 
                    (testPaint.measureText(text) > availableWidth) 
                    ) {
                trySize -= 2; //减小2个单位大小
                FontMetrics fm = testPaint.getFontMetrics();
                float scaled1 = (float) (this.getHeight() / (Math.ceil(fm.descent - fm.top) + 2));  
                float scaled2 = (float) ((testPaint.measureText(text) / availableWidth)); 
                if (scaled1 >= 1.75 & scaled1 >= scaled2) {
                    break;
                }
                if (trySize <= minTextSize) {
                    trySize = minTextSize;
                    break;
                }else if (trySize >= maxTextSize) {
                    trySize = maxTextSize;
                    break;
                }
                testPaint.setTextSize(trySize * scaled);
            }
            this.setTextSize(trySize); 
        }
    };
}

package me.grantland.widget;

import android.content.Context;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.widget.TextView;

/**
 * A {@link TextView} that re-sizes its text to be no larger than the width of the view.
 *
 * @attr ref R.styleable.AutofitTextView_sizeToFit
 * @attr ref R.styleable.AutofitTextView_minTextSize
 * @attr ref R.styleable.AutofitTextView_precision
 */
public class AutofitTextView extends TextView implements AutofitHelper.OnTextSizeChangeListener {

    private AutofitHelper mHelper;

    public AutofitTextView(Context context) {
        super(context);
        init(context, null, 0);
    }

    public AutofitTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs, 0);
    }

    public AutofitTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(context, attrs, defStyle);
    }

    private void init(Context context, AttributeSet attrs, int defStyle) {
        mHelper = AutofitHelper.create(this, attrs, defStyle)
                .addOnTextSizeChangeListener(this);
    }

    // Getters and Setters

    /**
     * {@inheritDoc}
     */
    @Override
    public void setTextSize(int unit, float size) {
        super.setTextSize(unit, size);
        if (mHelper != null) {
            mHelper.setTextSize(unit, size);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setLines(int lines) {
        super.setLines(lines);
        if (mHelper != null) {
            mHelper.setMaxLines(lines);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setMaxLines(int maxLines) {
        super.setMaxLines(maxLines);
        if (mHelper != null) {
            mHelper.setMaxLines(maxLines);
        }
    }

    /**
     * Returns the {@link AutofitHelper} for this View.
     */
    public AutofitHelper getAutofitHelper() {
        return mHelper;
    }

    /**
     * Returns whether or not the text will be automatically re-sized to fit its constraints.
     */
    public boolean isSizeToFit() {
        return mHelper.isEnabled();
    }

    /**
     * Sets the property of this field (sizeToFit), to automatically resize the text to fit its
     * constraints.
     */
    public void setSizeToFit() {
        setSizeToFit(true);
    }

    /**
     * If true, the text will automatically be re-sized to fit its constraints; if false, it will
     * act like a normal TextView.
     *
     * @param sizeToFit
     */
    public void setSizeToFit(boolean sizeToFit) {
        mHelper.setEnabled(sizeToFit);
    }

    /**
     * Returns the maximum size (in pixels) of the text in this View.
     */
    public float getMaxTextSize() {
        return mHelper.getMaxTextSize();
    }

    /**
     * Set the maximum text size to the given value, interpreted as "scaled pixel" units. This size
     * is adjusted based on the current density and user font size preference.
     *
     * @param size The scaled pixel size.
     *
     * @attr ref android.R.styleable#TextView_textSize
     */
    public void setMaxTextSize(float size) {
        mHelper.setMaxTextSize(size);
    }

    /**
     * Set the maximum text size to a given unit and value. See TypedValue for the possible
     * dimension units.
     *
     * @param unit The desired dimension unit.
     * @param size The desired size in the given units.
     *
     * @attr ref android.R.styleable#TextView_textSize
     */
    public void setMaxTextSize(int unit, float size) {
        mHelper.setMaxTextSize(unit, size);
    }

    /**
     * Returns the minimum size (in pixels) of the text in this View.
     */
    public float getMinTextSize() {
        return mHelper.getMinTextSize();
    }

    /**
     * Set the minimum text size to the given value, interpreted as "scaled pixel" units. This size
     * is adjusted based on the current density and user font size preference.
     *
     * @param minSize The scaled pixel size.
     *
     * @attr ref me.grantland.R.styleable#AutofitTextView_minTextSize
     */
    public void setMinTextSize(int minSize) {
        mHelper.setMinTextSize(TypedValue.COMPLEX_UNIT_SP, minSize);
    }

    /**
     * Set the minimum text size to a given unit and value. See TypedValue for the possible
     * dimension units.
     *
     * @param unit The desired dimension unit.
     * @param minSize The desired size in the given units.
     *
     * @attr ref me.grantland.R.styleable#AutofitTextView_minTextSize
     */
    public void setMinTextSize(int unit, float minSize) {
        mHelper.setMinTextSize(unit, minSize);
    }

    /**
     * Returns the amount of precision used to calculate the correct text size to fit within its
     * bounds.
     */
    public float getPrecision() {
        return mHelper.getPrecision();
    }

    /**
     * Set the amount of precision used to calculate the correct text size to fit within its
     * bounds. Lower precision is more precise and takes more time.
     *
     * @param precision The amount of precision.
     */
    public void setPrecision(float precision) {
        mHelper.setPrecision(precision);
    }

    @Override
    public void onTextSizeChange(float textSize, float oldTextSize) {
        // do nothing
    }
}