Android实现梯形TextView效果

public class LadderTextView extends android.support.v7.widget.AppCompatTextView { private static final String TAG = 'LadderView'; private Path linePath; private Paint paint, textPaint; private int width, height; private float strokeWidth = 2; private Region mRegion; private String textContent; private int lineOffset = 0;//划线的偏移量 private int textOffset = 0;//文本的偏移量 private float offsetScale = 1;//梯高与（梯顶与梯底）之差的比例（梯底比梯顶长） private boolean isLeft = true;//分为左和右两种斜角梯形模式 private boolean isSelected = false;//是否是选定 private int selectedColor = Color.BLACK; public LadderTextView(Context context) {super(context);init(); } public LadderTextView(Context context, AttributeSet attrs) {super(context, attrs);initAttributes(context, attrs);init(); } public LadderTextView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);initAttributes(context, attrs);init(); } private void initAttributes(Context context, AttributeSet attrs) {TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.LadderTextView);textContent = typedArray.getString(R.styleable.LadderTextView_textContent);offsetScale = typedArray.getFloat(R.styleable.LadderTextView_offsetScale, 0.5f);isLeft = typedArray.getBoolean(R.styleable.LadderTextView_isLeft, true);isSelected = typedArray.getBoolean(R.styleable.LadderTextView_isSelected, true);selectedColor = typedArray.getColor(R.styleable.LadderTextView_selectedColor, Color.GREEN);strokeWidth = typedArray.getDimension(R.styleable.LadderTextView_strokeWidth, 1);typedArray.recycle(); } private void init() {Log.v(TAG, 'init');mRegion = new Region();paint = new Paint();textPaint = new Paint();linePath = new Path();paint.setAntiAlias(true);paint.setStrokeWidth(dp2px(getContext(), strokeWidth));paint.setColor(selectedColor);paint.setStyle(isSelected ? Paint.Style.FILL_AND_STROKE : Paint.Style.STROKE);paint.setStrokeJoin(Paint.Join.ROUND);textPaint.setAntiAlias(true);textPaint.setTextSize(getTextSize());//传递TextSize(px)textPaint.setColor(isSelected ? Color.WHITE : selectedColor);setText('');//去除掉原有的Text内容lineOffset = dp2px(getContext(), strokeWidth) / 2;textOffset = (int) (getTextSize() / 2) + getBaseline() * 2;Log.v(TAG, 'lineOffset textOffset ->' + lineOffset + ' ' + textOffset); } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) {super.onLayout(changed, left, top, right, bottom);width = getWidth();height = getHeight();Log.v(TAG, 'width height->' + width + ' ' + height); } @Override protected void onDraw(Canvas canvas) {super.onDraw(canvas);Log.v(TAG, 'onDraw');if (isLeft) { linePath.moveTo(0 + lineOffset, 0 + lineOffset); linePath.lineTo(width, 0 + lineOffset); linePath.lineTo((int) (width - offsetScale * height), height - lineOffset); linePath.lineTo(0 + lineOffset, height - lineOffset); linePath.close(); setTextAlignment(TEXT_ALIGNMENT_TEXT_START); canvas.drawPath(linePath, paint); canvas.drawText(textContent == null ? '' : textContent, getPaddingStart() + lineOffset, height / 2 + textOffset, textPaint);} else { linePath.moveTo(0 + lineOffset + offsetScale * height, 0 + lineOffset); linePath.lineTo(width - lineOffset, 0 + lineOffset); linePath.lineTo(width - lineOffset, height - lineOffset); linePath.lineTo(0, height - lineOffset); linePath.close(); setTextAlignment(TEXT_ALIGNMENT_TEXT_END); canvas.drawPath(linePath, paint); canvas.drawText(textContent == null ? '' : textContent, getWidth() - lineOffset - getPaddingEnd() - getDrawTextWidth(textPaint, textContent), height / 2 + textOffset, textPaint);} } @Override public boolean dispatchTouchEvent(MotionEvent event) {if (event.getAction() == MotionEvent.ACTION_DOWN) { if (!isInRegion(event)) {//点击的点的位置不在范围内则不响应return false; }}return super.dispatchTouchEvent(event); } /** * 判断点击的位置是否在要求的范围内 * @param event * @return */ public boolean isInRegion(MotionEvent event) {RectF rectF = new RectF();linePath.computeBounds(rectF, true);mRegion.setPath(linePath, new Region((int) rectF.left, (int) rectF.top, (int) rectF.right, (int) rectF.bottom));return mRegion.contains((int) event.getX(), (int) event.getY()); } /** * 获取要画的字符串的宽度 * * @param paint * @param textContent * @return */ private int getDrawTextWidth(Paint paint, String textContent) {float totalWidth = 0f;if (textContent != null && textContent.length() > 0) { int len = textContent.length(); float[] widths = new float[len]; paint.getTextWidths(textContent, widths); for (int j = 0; j < len; j++) {totalWidth += widths[j]; }}return (int) Math.ceil(totalWidth); } /** * @param dpValue （DisplayMetrics类中属性density） * @return */ private int dp2px(Context context, float dpValue) {final float scale = context.getResources().getDisplayMetrics().density;return (int) (dpValue * scale + 0.5f); } public void setTextContent(String textContent) {this.textContent = textContent;invalidate(); } public void setMSelected(boolean isSelected) {textPaint.setColor(isSelected ? Color.WHITE : selectedColor);paint.setStyle(isSelected ? Paint.Style.FILL_AND_STROKE : Paint.Style.STROKE);this.isSelected = isSelected;invalidate(); } @Override public boolean isSelected() {return isSelected; }}要点分析1.背景与文本内容的绘制

计算好四个点的位置连线，TextView默认的文本内容则设置为空字符串，采用drawText的方式来实现文本的显示。需要注意的是计算文本的字号长度大小、颜色以及位于整个view的位置、偏移量等。

依照于设计，梯形内的点击才有响应，则要计算点击的位置是否在梯形内，然后通过dispatchTouchEvent来做事件的分发。

/** * 判断点击的位置是否在要求的范围内 * @param event * @return */ public boolean isInRegion(MotionEvent event) {RectF rectF = new RectF();linePath.computeBounds(rectF, true);mRegion.setPath(linePath, new Region((int) rectF.left, (int) rectF.top, (int) rectF.right, (int) rectF.bottom));return mRegion.contains((int) event.getX(), (int) event.getY()); }3.其它自定义属性

依据于需求来定，注意invalidate。

最后，完整代码

https://github.com/ganshenml/LadderTextView

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