笔记11 | 动态更改TextView的字体大小

地址

一个常用的知识点：动态设置TextView的大小的工具，需要动态更改的TextView的内容字体的大小，比如设定的TextView的只有一行，宽度只有200dp，内容超过这个之后就缩小字体显示，只能能将字体都显示完全;也就是动态更改的的TextView的字体大小，当TextView的的的内容比较多时缩小显示，当TextView的中的内容比较少时正常显示

目录

• 图片展示

• 方法一：重写的TextView

• 方法二：使用框架Android的autofittextview

---

图片展示

可以看出来：当文字没有填充的TextView的完全时显示的就是默认的字体，当文字能够完全填充的TextView的并且一行显示不下时，他会默认的缩小文字的字体，当文字再多时，他会默认在末尾省略。

---

方法一：重写的TextView

此类方法是在的TextView的onTextChanged和onSizeChanged下，根据获取的TextView可容纳的宽度来计算一个靠近可容纳的最大字体宽度，从而来给TextView的设置textsize。

public class CustomTextView extends TextView {
	
	/*
	 * Even add it by 20170518 
	 * dynamic setting textview's width and textsize Demo
	 * 
	 */
	
	/*
	 * 定义字体大小边界值
	 */
	private static float DEFAULT_MIN_TEXT_SIZE = 1; 
	private static float DEFAULT_MAX_TEXT_SIZE = 48;
	
	// Attributes
	private Paint testPaint; //此类包含如何绘制的样式和颜色信息
	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);
		}
	}
	
	private void refitText(String text, int textWidth) {

		if (textWidth > 0) {
			int availableWidth = textWidth - this.getPaddingLeft()
					- this.getPaddingRight();       
			float trySize = TextSize; 
			float scaled = getContext().getResources().getDisplayMetrics().scaledDensity;
			testPaint.setTextSize(trySize * scaled);//给testPaint设置 dp转为px后的textsize
			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); 
		}
	};
}

---

方法二：使用框架Android的autofittextview

框架地址：HTTPS：//github.com/grantland/android-autofittextview

AutofitTextView：自定义的TextView的并继承系统的的TextView的，然后在绘制组件的时候根据getMaxLines方法获取内容的行数若内容的行数大于1，则缩小文字的字体，然后在尝试获取getMaxLines方法，若内容的行数还是大于1，则缩小文字的字体，直到内容能够一行显示或者是字体缩小大一定的大小，这时候若缩小到一定的大小还是不能一行显示，则尾部省略。

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
    }
}