Android动态更改TextView的字体大小

Android动态更改TextView的字体大小

需求：

需要动态更改TextView内容字体的大小，比如设定TextView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TextView的字体大小，当TextView的内容比较多时缩小显示，当TextView的内容比较少时正常显示。

使用框架:Android-autofittextview 地址：​​​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 * @attrpublic 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 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 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 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 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 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 public void setPrecision(float precision) { mHelper.setPrecision(precision); } @Override public void onTextSizeChange(float textSize, float oldTextSize) { // do nothing

原理：

AutofitTextView：自定义TextView并继承系统的TextView，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。

延伸： TextView源码中：

public void setTextSize(float size) { setTextSize(TypedValue.COMPLEX_UNIT_SP, size); }public void setTextSize(int unit, float size) { Context c = getContext(); Resources r; if (c == null) r = Resources.getSystem(); else

setTextSize(int unit, int size) 第一个参数可设置如下静态变量： TypedValue.COMPLEX_UNIT_PX : Pixels TypedValue.COMPLEX_UNIT_SP : Scaled Pixels TypedValue.COMPLEX_UNIT_DIP : Device Independent Pixels

我们在使用TextView控件时，调用setTextSize方法，默认就是以sp为单位，与xml配置文件默认保存一致。

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