Edittexth和TextView字体大小跟随输入长度自动缩放

33.Android 自动适配字体大小的AutoAdjustSizeEditText

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AutoAdjustSizeEditText介绍

由于一个需求，就是一个定宽高的EditText里，输入后，要根据字的内容改变字体大小。

这时候就需要这么一个自定适配字体大小的EditView。

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AutoAdjustSizeEditText原理

实现原理： 重写EditText，覆写其setText、onTextChanged和onSizeChanged方法。分别在这里重新写适配字体大小的逻辑处理，所谓的逻辑处理，就是计算单行可见文字的宽度，然后从自定义的最大字体开始尝试，先用最大字体去写字（ Paint.setTextSize(float textSize) ），然后判断：最大字体画出字的宽度>可见文字宽度。如果成立，那么减小一号字体再去画，不断去减小字体去判断，直到不成立时，就找到合适的字体大小了。

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AutoAdjustSizeEditText

public class AutoAdjustSizeEditText extends EditText {    // 最小字体    private static final float DEFAULT_MIN_TEXT_SIZE = 8.0f;    // 最大字体    private static final float DEFAULT_MAX_TEXT_SIZE = 16.0f;    private Paint textPaint;    private float minTextSize = DEFAULT_MIN_TEXT_SIZE;    private float maxTextSize = DEFAULT_MAX_TEXT_SIZE;    public AutoAdjustSizeEditText(Context context, AttributeSet attrs) {        super(context, attrs);    }    private void initialise() {        DisplayMetrics displayMetrics = this.getResources().getDisplayMetrics();        if (this.textPaint == null) {            this.textPaint = new Paint();            this.textPaint.set(this.getPaint());        }        this.maxTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, this.maxTextSize, displayMetrics);        if (DEFAULT_MIN_TEXT_SIZE >= maxTextSize) {            this.maxTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, this.maxTextSize, displayMetrics);        }        this.maxTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, this.maxTextSize, displayMetrics);        this.minTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, this.minTextSize, displayMetrics);    }    /**     * Re size the font so the specified text fits in the text box * assuming     * the text box is the specified width.     */    private void fitText(String text, int textWidth) {        if (textWidth > 0) {            // 单行可见文字宽度            int availableWidth = textWidth - this.getPaddingLeft() - this.getPaddingRight();            float trySize = maxTextSize;            // 先用最大字体写字            textPaint.setTextSize(trySize);            // 如果最大字体>最小字体 && 最大字体画出字的宽度>单行可见文字宽度            while ((trySize > minTextSize) && (textPaint.measureText(text) > availableWidth)) {                // 最大字体小一号                trySize -= 1;                // 保证大于最小字体                if (trySize <= minTextSize) {                    trySize = minTextSize;                    break;                }                // 再次用新字体写字                textPaint.setTextSize(trySize);            }            this.setTextSize(trySize);        }    }    /**     * 重写setText     * 每次setText的时候     *     * @param text     * @param type     */    @Override    public void setText(CharSequence text, BufferType type) {        this.initialise();        String textString = text.toString();        float trySize = maxTextSize;        if (this.textPaint == null) {            this.textPaint = new Paint();            this.textPaint.set(this.getPaint());        }        this.textPaint.setTextSize(trySize);        // 计算设置内容前 内容占据的宽度        int textWidth = (int) this.textPaint.measureText(textString);        // 拿到宽度和内容，进行调整        this.fitText(textString, textWidth);        super.setText(text, type);    }    @Override    protected void onTextChanged(CharSequence text, int start, int before, int after) {        super.onTextChanged(text, start, before, after);        this.fitText(text.toString(), this.getWidth());    }    /**     * This is called during layout when the size of this view has changed. If     * you were just added to the view hierarchy, you're called with the old     * values of 0.     *     * @param w    Current width of this view.     * @param h    Current height of this view.     * @param oldw Old width of this view.     * @param oldh Old height of this view.     */    @Override    protected void onSizeChanged(int w, int h, int oldw, int oldh) {        // 如果当前view的宽度 != 原来view的宽度        if (w != oldw) this.fitText(this.getText().toString(), w);    }}
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AutoAdjustSizeEditTextActivity

AutoAdjustSizeEditTextActivity

public class AutoAdjustSizeEditTextActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        this.setContentView(R.layout.activity_auto_adjust_size_edit_text);    }}
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activity_auto_adjust_size_edit_text.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <camnter.newlife.widget.AutoAdjustSizeEditText        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything"        android:textColor="#ffFF4081" />    <camnter.newlife.widget.AutoAdjustSizeEditText        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything Save you from anything"        android:textColor="#ffFF4081" />    <camnter.newlife.widget.AutoAdjustSizeEditText        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything Save you from anything Save you from anything "        android:textColor="#ffFF4081" />    <camnter.newlife.widget.AutoAdjustSizeEditText        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything Save you from anything Save you from anything Save you from anything "        android:textColor="#ffFF4081" />    <camnter.newlife.widget.AutoAdjustSizeEditText        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything Save you from anything Save you from anything Save you from anything Save you from anything "        android:textColor="#ffFF4081" /></LinearLayout>
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AutoAdjustSizeEditTextActivity效果图

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AutoAdjustSizeTextView

由于，EditText也是TextView的子类，所以用上面的AutoAdjustSizeEditText代码一样可以实现自动适配字体大小的TextView。

public class AutoAdjustSizeTextView extends TextView {    // 最小字体    private static final float DEFAULT_MIN_TEXT_SIZE = 8.0f;    // 最大字体    private static final float DEFAULT_MAX_TEXT_SIZE = 16.0f;    private Paint textPaint;    private float minTextSize = DEFAULT_MIN_TEXT_SIZE;    private float maxTextSize = DEFAULT_MAX_TEXT_SIZE;    public AutoAdjustSizeTextView(Context context, AttributeSet attrs) {        super(context, attrs);    }    private void initialise() {        DisplayMetrics displayMetrics = this.getResources().getDisplayMetrics();        if (this.textPaint == null) {            this.textPaint = new Paint();            this.textPaint.set(this.getPaint());        }        this.maxTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, this.maxTextSize, displayMetrics);        if (DEFAULT_MIN_TEXT_SIZE >= maxTextSize) {            this.maxTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, this.maxTextSize, displayMetrics);        }        this.maxTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, this.maxTextSize, displayMetrics);        this.minTextSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, this.minTextSize, displayMetrics);    }    /**     * Re size the font so the specified text fits in the text box * assuming     * the text box is the specified width.     */    private void fitText(String text, int textWidth) {        if (textWidth > 0) {            // 单行可见文字宽度            int availableWidth = textWidth - this.getPaddingLeft() - this.getPaddingRight();            float trySize = maxTextSize;            // 先用最大字体写字            textPaint.setTextSize(trySize);            // 如果最大字体>最小字体 && 最大字体画出字的宽度>单行可见文字宽度            while ((trySize > minTextSize) && (textPaint.measureText(text) > availableWidth)) {                // 最大字体小一号                trySize -= 1;                // 保证大于最小字体                if (trySize <= minTextSize) {                    trySize = minTextSize;                    break;                }                // 再次用新字体写字                textPaint.setTextSize(trySize);            }            this.setTextSize(trySize);        }    }    /**     * 重写setText     * 每次setText的时候     *     * @param text     * @param type     */    @Override    public void setText(CharSequence text, BufferType type) {        this.initialise();        String textString = text.toString();        float trySize = maxTextSize;        if (this.textPaint == null) {            this.textPaint = new Paint();            this.textPaint.set(this.getPaint());        }        this.textPaint.setTextSize(trySize);        // 计算设置内容前 内容占据的宽度        int textWidth = (int) this.textPaint.measureText(textString);        // 拿到宽度和内容，进行调整        this.fitText(textString, textWidth);        super.setText(text, type);    }    @Override    protected void onTextChanged(CharSequence text, int start, int before, int after) {        super.onTextChanged(text, start, before, after);        this.fitText(text.toString(), this.getWidth());    }    /**     * This is called during layout when the size of this view has changed. If     * you were just added to the view hierarchy, you're called with the old     * values of 0.     *     * @param w    Current width of this view.     * @param h    Current height of this view.     * @param oldw Old width of this view.     * @param oldh Old height of this view.     */    @Override    protected void onSizeChanged(int w, int h, int oldw, int oldh) {        // 如果当前view的宽度 != 原来view的宽度        if (w != oldw) this.fitText(this.getText().toString(), w);    }}
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AutoAdjustSizeTextViewActivity

AutoAdjustSizeTextViewActivity

public class AutoAdjustSizeTextViewActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        this.setContentView(R.layout.activity_auto_adjust_size_text_view);    }}
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activity_auto_adjust_size_text_view.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <camnter.newlife.widget.AutoAdjustSizeTextView        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything"        android:textColor="#ffFF4081" />    <camnter.newlife.widget.AutoAdjustSizeTextView        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything Save you from anything"        android:textColor="#ffFF4081" />    <camnter.newlife.widget.AutoAdjustSizeTextView        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything Save you from anything Save you from anything "        android:textColor="#ffFF4081" />    <camnter.newlife.widget.AutoAdjustSizeTextView        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything Save you from anything Save you from anything Save you from anything "        android:textColor="#ffFF4081" />    <camnter.newlife.widget.AutoAdjustSizeTextView        android:layout_width="160dp"        android:layout_height="wrap_content"        android:layout_margin="16dp"        android:padding="16dp"        android:text="Save you from anything Save you from anything Save you from anything Save you from anything Save you from anything "        android:textColor="#ffFF4081" /></LinearLayout>
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AutoAdjustSizeTextViewActivity效果图

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