TextView两端对齐

不念不忘少年蓝@ 2022-06-07 01:22 335阅读 0赞

# 在res文件加下添加attrs.xml文件，用于设置styleable #

<?xml version="1.0" encoding="utf-8"?>
    <resources>
        
        <declare-styleable name="AlignTextView">
            <attr name="align" format="enum">
                <enum name="left" value="0"/>
                <enum name="center" value="1"/>
                <enum name="right" value="2"/>
            </attr>
        </declare-styleable>
    </resources>

# 自定义AlignTextView.java类，继承自TextView #

import android.content.Context;
    import android.content.res.TypedArray;
    import android.graphics.Canvas;
    import android.graphics.Paint;
    import android.text.TextPaint;
    import android.util.AttributeSet;
    import android.util.TypedValue;
    import android.widget.TextView;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /** * 两端对齐的text view，可以设置最后一行靠左，靠右，居中对齐 * * @author YD */
    public class AlignTextView extends TextView { 
        private float textHeight; // 单行文字高度
        private float textLineSpaceExtra = 0; // 额外的行间距
        private int width; // textView宽度
        private List<String> lines = new ArrayList<String>(); // 分割后的行
        private List<Integer> tailLines = new ArrayList<Integer>(); // 尾行
        private Align align = Align.ALIGN_LEFT; // 默认最后一行左对齐
        private boolean firstCalc = true;  // 初始化计算
    
        private float lineSpacingMultiplier = 1.0f;
        private float lineSpacingAdd = 0.0f;
    
        private int originalHeight = 0; //原始高度
        private int originalLineCount = 0; //原始行数
        private int originalPaddingBottom = 0; //原始paddingBottom
        private boolean setPaddingFromMe = false;
    
        // 尾行对齐方式
        public enum Align {
            ALIGN_LEFT, ALIGN_CENTER, ALIGN_RIGHT  // 居中，居左，居右,针对段落最后一行
        }
    
        public AlignTextView(Context context) {
            super(context);
            setTextIsSelectable(false);
        }
    
        public AlignTextView(Context context, AttributeSet attrs) {
            super(context, attrs);
            setTextIsSelectable(false);
    
            lineSpacingMultiplier = attrs.getAttributeFloatValue("http://schemas.android" + "" +
                    ".com/apk/res/android", "lineSpacingMultiplier", 1.0f);
    
            int[] attributes = new int[]{android.R.attr.lineSpacingExtra};
    
            TypedArray arr = context.obtainStyledAttributes(attrs, attributes);
    
            lineSpacingAdd = arr.getDimensionPixelSize(0, 0);
    
            originalPaddingBottom = getPaddingBottom();
    
            TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.AlignTextView);
    
            int alignStyle = ta.getInt(R.styleable.AlignTextView_align, 0);
            switch (alignStyle) {
                case 1:
                    align = Align.ALIGN_CENTER;
                    break;
                case 2:
                    align = Align.ALIGN_RIGHT;
                    break;
                default:
                    align = Align.ALIGN_LEFT;
                    break;
            }
    
            ta.recycle();
        }
    
    
        @Override
        protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
            super.onLayout(changed, left, top, right, bottom);
    
            //首先进行高度调整
            if (firstCalc) {
                width = getMeasuredWidth();
                String text = getText().toString();
                TextPaint paint = getPaint();
                lines.clear();
                tailLines.clear();
    
                // 文本含有换行符时，分割单独处理
                String[] items = text.split("\\n");
                for (String item : items) {
                    calc(paint, item);
                }
    
                //使用替代textview计算原始高度与行数
                measureTextViewHeight(text, paint.getTextSize(), getMeasuredWidth() -
                        getPaddingLeft() - getPaddingRight());
    
                //获取行高
                textHeight = 1.0f * originalHeight / originalLineCount;
    
                textLineSpaceExtra = textHeight * (lineSpacingMultiplier - 1) + lineSpacingAdd;
    
                //计算实际高度,加上多出的行的高度(一般是减少)
                int heightGap = (int) ((textLineSpaceExtra + textHeight) * (lines.size() -
                        originalLineCount));
    
                setPaddingFromMe = true;
                //调整textview的paddingBottom来缩小底部空白
                setPadding(getPaddingLeft(), getPaddingTop(), getPaddingRight(),
                        originalPaddingBottom + heightGap);
    
                firstCalc = false;
            }
        }
    
        @Override
        protected void onDraw(Canvas canvas) {
            TextPaint paint = getPaint();
            paint.setColor(getCurrentTextColor());
            paint.drawableState = getDrawableState();
    
            width = getMeasuredWidth();
    
            Paint.FontMetrics fm = paint.getFontMetrics();
            float firstHeight = getTextSize() - (fm.bottom - fm.descent + fm.ascent - fm.top);
    
            int gravity = getGravity();
            if ((gravity & 0x1000) == 0) { // 是否垂直居中
                firstHeight = firstHeight + (textHeight - firstHeight) / 2;
            }
    
            int paddingTop = getPaddingTop();
            int paddingLeft = getPaddingLeft();
            int paddingRight = getPaddingRight();
            width = width - paddingLeft - paddingRight;
    
            for (int i = 0; i < lines.size(); i++) {
                float drawY = i * textHeight + firstHeight;
                String line = lines.get(i);
                // 绘画起始x坐标
                float drawSpacingX = paddingLeft;
                float gap = (width - paint.measureText(line));
                float interval = gap / (line.length() - 1);
    
                // 绘制最后一行
                if (tailLines.contains(i)) {
                    interval = 0;
                    if (align == Align.ALIGN_CENTER) {
                        drawSpacingX += gap / 2;
                    } else if (align == Align.ALIGN_RIGHT) {
                        drawSpacingX += gap;
                    }
                }
    
                for (int j = 0; j < line.length(); j++) {
                    float drawX = paint.measureText(line.substring(0, j)) + interval * j;
                    canvas.drawText(line.substring(j, j + 1), drawX + drawSpacingX, drawY +
                            paddingTop + textLineSpaceExtra * i, paint);
                }
            }
        }
    
        /** * 设置尾行对齐方式 * * @param align 对齐方式 */
        public void setAlign(Align align) {
            this.align = align;
            invalidate();
        }
    
        /** * 计算每行应显示的文本数 * * @param text 要计算的文本 */
        private void calc(Paint paint, String text) {
            if (text.length() == 0) {
                lines.add("\n");
                return;
            }
            int startPosition = 0; // 起始位置
            float oneChineseWidth = paint.measureText("中");
            int ignoreCalcLength = (int) (width / oneChineseWidth); // 忽略计算的长度
            StringBuilder sb = new StringBuilder(text.substring(0, Math.min(ignoreCalcLength + 1,
                    text.length())));
    
            for (int i = ignoreCalcLength + 1; i < text.length(); i++) {
                if (paint.measureText(text.substring(startPosition, i + 1)) > width) {
                    startPosition = i;
                    //将之前的字符串加入列表中
                    lines.add(sb.toString());
    
                    sb = new StringBuilder();
    
                    //添加开始忽略的字符串，长度不足的话直接结束,否则继续
                    if ((text.length() - startPosition) > ignoreCalcLength) {
                        sb.append(text.substring(startPosition, startPosition + ignoreCalcLength));
                    } else {
                        lines.add(text.substring(startPosition));
                        break;
                    }
    
                    i = i + ignoreCalcLength - 1;
                } else {
                    sb.append(text.charAt(i));
                }
            }
            if (sb.length() > 0) {
                lines.add(sb.toString());
            }
    
            tailLines.add(lines.size() - 1);
        }
    
    
        @Override
        public void setText(CharSequence text, BufferType type) {
            firstCalc = true;
            super.setText(text, type);
        }
    
        @Override
        public void setPadding(int left, int top, int right, int bottom) {
            if (!setPaddingFromMe) {
                originalPaddingBottom = bottom;
            }
            setPaddingFromMe = false;
            super.setPadding(left, top, right, bottom);
        }
    
    
        /** * 获取文本实际所占高度，辅助用于计算行高,行数 * * @param text 文本 * @param textSize 字体大小 * @param deviceWidth 屏幕宽度 */
        private void measureTextViewHeight(String text, float textSize, int deviceWidth) {
            TextView textView = new TextView(getContext());
            textView.setText(text);
            textView.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize);
            int widthMeasureSpec = MeasureSpec.makeMeasureSpec(deviceWidth, MeasureSpec.EXACTLY);
            int heightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
            textView.measure(widthMeasureSpec, heightMeasureSpec);
            originalLineCount = textView.getLineCount();
            originalHeight = textView.getMeasuredHeight();
        }
    }

# activity\_main.xml布局中添加一个普通的TextView，添加一个AlignTextView #

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:orientation="vertical" tools:context="com.zcn.demo.aligntextview.MainActivity">
    
        <TextView android:id="@+id/text" android:layout_width="wrap_content" android:layout_height="wrap_content"/>
    
        
        <com.zcn.demo.aligntextview.AlignTextView android:id="@+id/text1" android:layout_width="wrap_content" android:layout_height="wrap_content" />
    </LinearLayout>

# AlignTextViews的使用和正常的TextView使用一样 #

public class MainActivity extends AppCompatActivity { 
        private AlignTextView alignText;
        private TextView text;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            text = (TextView)findViewById(R.id.text);
            text.setText("这个是测试文本，用于观察现象，做对比使用，this is test text,for to see the different in different Controls");
    
            alignText = (AlignTextView)findViewById(R.id.text1);
            alignText.setText("这个是测试文本，用于观察现象，做对比使用，this is test text,for to see the different in different Controls");
        }
    }