如果你打算完全定制一個(gè)View，那么你需要實(shí)現(xiàn)View類（所有的Android?View都實(shí)現(xiàn)于這個(gè)類），并且實(shí)現(xiàn)確定尺寸的onMeasure(…))方法和確認(rèn)繪圖的onDraw(…))方法。

自定義View一共分為6步

第一步

public class SmileyView extends View {private Paint mCirclePaint;private Paint mEyeAndMouthPaint;private float mCenterX;private float mCenterY;private float mRadius;private RectF mArcBounds = new RectF();public SmileyView(Context context) {this(context, null);}public SmileyView(Context context, AttributeSet attrs) {this(context, attrs, 0);}public SmileyView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);initPaints();}private void initPaints() {/* ... */}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {/* ... */}@Overrideprotected void onDraw(Canvas canvas) {/* ... */} }

2.實(shí)現(xiàn)畫筆paint類

本文一共兩只畫筆

private void initPaints() {mCirclePaint = new Paint(Paint.ANTI_ALIAS_FLAG);mCirclePaint.setStyle(Paint.Style.FILL);mCirclePaint.setColor(Color.YELLOW);mEyeAndMouthPaint = new Paint(Paint.ANTI_ALIAS_FLAG);mEyeAndMouthPaint.setStyle(Paint.Style.STROKE);mEyeAndMouthPaint.setStrokeWidth(16 * getResources().getDisplayMetrics().density);mEyeAndMouthPaint.setStrokeCap(Paint.Cap.ROUND);mEyeAndMouthPaint.setColor(Color.BLACK); }

3.覆寫onMeasure(…)方法

實(shí)現(xiàn)這個(gè)方法告訴了母容器如何放棄自定義View，可以通過提供的measureSpecs來決定你的View的高和寬，以下是一個(gè)正方形，確認(rèn)它的寬和高是一樣的。

@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {int w = MeasureSpec.getSize(widthMeasureSpec);int h = MeasureSpec.getSize(heightMeasureSpec);int size = Math.min(w, h);setMeasuredDimension(size, size); }

注意：

這個(gè)方法需要至少保證一個(gè)setMeasuredDimension(..)調(diào)用，否則會(huì)報(bào)IllegalStateException錯(cuò)誤。

4.實(shí)現(xiàn)onSizeChanged(…)方法

這個(gè)方法是你獲取View現(xiàn)在的寬和高. 這里我們計(jì)算的是中心和半徑。

@Override protected void onSizeChanged(int w, int h, int oldw, int oldh) {mCenterX = w / 2f;mCenterY = h / 2f;mRadius = Math.min(w, h) / 2f; }

5.實(shí)現(xiàn)onDraw(…)方法

這個(gè)方法提供了如何繪制view，它提供的Canvas類可以進(jìn)行繪制。

@Override protected void onDraw(Canvas canvas) {// draw facecanvas.drawCircle(mCenterX, mCenterY, mRadius, mCirclePaint);// draw eyesfloat eyeRadius = mRadius / 5f;float eyeOffsetX = mRadius / 3f;float eyeOffsetY = mRadius / 3f;canvas.drawCircle(mCenterX - eyeOffsetX, mCenterY - eyeOffsetY, eyeRadius, mEyeAndMouthPaint);canvas.drawCircle(mCenterX + eyeOffsetX, mCenterY - eyeOffsetY, eyeRadius, mEyeAndMouthPaint);// draw mouthfloat mouthInset = mRadius /3f;mArcBounds.set(mouthInset, mouthInset, mRadius * 2 - mouthInset, mRadius * 2 - mouthInset);canvas.drawArc(mArcBounds, 45f, 90f, false, mEyeAndMouthPaint); }

6.添加你的View

<FrameLayoutxmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"><com.example.app.SmileyViewandroid:layout_width="match_parent"android:layout_height="match_parent" /> </FrameLayout>

到此就結(jié)束了，自定義View沒你想的那么難

轉(zhuǎn)載自：Android開發(fā)中文站???Android-6步教你自定義View

轉(zhuǎn)載于:https://www.cnblogs.com/yuezhusust/p/6549318.html

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