編輯:關於Android編程
3.1 Android控件架構 3.2 View的測量 3.3 View的繪制 3.4 ViewGroup的測量 3.5 ViewGroup的繪制 3.6 自定義View
3.6.1 對現有的空間進行拓展 3.6.2 創建復合控件 3.6.3 重寫View來實現全新的空間 3.7 自定義ViewGroup 3.8 事件攔截機制分析
控件大致非為兩類:
view控件:視圖控件 viewGroup控件:包含多個View控件,並管理其包含的View控件 兩者之間的關系:上層控件負責下層子控件的測量與繪制,並傳遞交互事件UI界面架構:
Activity都包含一個Window對象,通常由PhoneWindow來實現 PhoneWindow將一個DecorView設置為整個應用窗口的根View
DecorView為整個Window界面的最頂層View DecorView只有一個子元素為LinearLayout,代表整個Window界面,包含通知欄,標題欄,內容顯示欄三塊區域 LinearLayout裡有兩個FrameLayout子元素:
標題欄顯示界面。只有一個TextView顯示應用的名稱 內容欄顯示界面。就是setContentView()方法載入的布局界面
MeasureSpec類:32位的int值,高2位為測量模式,低30位為測量大小
MeasureSpec模式:
EXACTLY:精確模式 ,當控件的layout_width屬性或layout_height屬性指定為具體值,控件大小也是該具體值 AT_MOST:最大值模式,當控件layout_width屬性或layout_height屬性指定為warp_content時,控件的尺寸不要超過父控件允許的最大尺寸 UNSPECIFIED:未指定模式,控件要多大就多大,通常情況下再繪制自定義View中才會使用View類默認的onMeasure()方法只支持EXACTLY模式,View需要支持warp_content屬性,那麼就必須重寫onMeasure()方法,來制定warp_content的大小
下面我們通過一個簡單的實例,演示如何進行View的測量,首先,需要重寫onMeasure()方法:
@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); }
可以發現,onMeasure方法調用了父類的onMeasure方法,代碼跟蹤父類onMeasure方法
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec), getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec)); }
可以發現,系統最終會調用setMeasuredDimension(int measuredWidth,int measuredHeight)方法將測量後的寬高值設置進去,我們調用自定義的measureWidth()方法和measureHeight()方法,分別對寬高進行重新定義
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { setMeasuredDimension(measureWidth(widthMeasureSpec),measureHeight(heightMeasureSpec)); }
下面以measureWidth()方法為例:
第一步:從MeasureSpec對象中提取出具體的測量模式和大小
int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec);
第二步:通過不同的測量模式給出不同的測量值:
EXACTLY:使用指定的specSize即可 AT_MOST:取出我們指定的大小和SpecSize的最小值 UNSPECIFIED:200px下面這段代碼基本上可以作為模板代碼:
private int measureWidth(int measureSpec) { int result = 0; int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec); if (specMode == MeasureSpec.EXACTLY) { result = specSize; } else { result = 200; if (specMode == MeasureSpec.AT_MOST) { result = Math.min(result, specSize); } } return result; }
可以發現,當指定warp_content屬性時,View就獲得一個默認值200px
當測量好了一個View之後,我們通過重寫View類中的onDraw()方法來繪圖,要想繪制相應的圖像,就必須在Canvas上進行繪制
Canvas canvas = new Canvas(Bitmap);
Canvas就像是一個畫板,我們傳進去一個bitmap,通過這個bitmap創建的Canvas畫布緊緊聯系在一起,這個過程我們稱之為裝載畫布,這個bitmap用來存儲所有繪制在Canvas上的像素信息,所以當你在後面調用所有的Canvas.drawxxx方法都會發生在這個bitmap上
ViewGroup在測量時通過遍歷所有子View,從而調用子View的Measure方法來獲得每一個子View的結果
@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); int childCount = getChildCount(); for (int i = 0; i < childCount; i++) { getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec); } }
ViewGroup測量完畢後,通常會去重寫onLayout()方法來控制其子View顯示位置的邏輯
@Override protected void onLayout(boolean changed, int l, int t, int r, int b) { for (int i = 0; i < getChildCount(); i++) { this.getChildAt(i).layout(l, t, r, b); } }
ViewGroup通常不需要繪制,如果不是指定ViewGroup的背景顏色,那麼ViewGroup的onDraw()方法都不會被調用,但是,ViewGroup會使用dispatchDraw()方法來繪制子View
@Override protected void dispatchDraw(Canvas canvas) { super.dispatchDraw(canvas); }
在View中通常有以下一些重要的回調方法:
onFinishInflate():從XML加載組件後回調 onSizeChanged():組件大小改變時回調 onMeasure():回調該方法來進行測量 onLayout():回調該方法來確定顯示的位置 onTouchEvent():監聽到觸摸事件時回調通常情況下,有以下三種方法來實現自定義的控件:
對現有的控件進行拓展 通過組合來實現新的控件 重寫View來實現全新的控件
3.6.1 對現有的控件進行拓展
自定義修改TextView……見經典代碼回顧,案例一 閃動的文字效果……見經典代碼回顧,案例二
3.6.2 創建復合控件
自定義ToolBar的實現……見經典代碼回顧,案例三
3.6.3 重寫View來實現全新的控件
弧線展示圖……見經典代碼回顧,案例四 音頻條形圖……見經典代碼回顧,案例五
自定義ViewGroup,仿ScrollView……見經典代碼回顧,案例六
事件攔截機制三個重要方法
dispatchTouchEvent():分發事件 onInterceptTouchEvent():攔截事件 onTouchEvent():處理事件舉一個例子說明事件分發機制:
ViewGroupA:處於視圖最下層 ViewGroupB:處於視圖中間層 View:處於視圖最上層正常的事件分發機制流程:
ViewGroupA dispatchTouchEvent ViewGroupA onInterceptTouchEvent ViewGroupB dispatchTouchEvent ViewGroupB onInterceptTouchEvent View dispatchTouchEvent View onTouchEvent ViewGroupB onTouchEvent ViewGroupA onTouchEvent若ViewGroupB的onInterceptTouchEvent()方法返回true的分發機制流程:
ViewGroupA dispatchTouchEvent ViewGroupA onInterceptTouchEvent ViewGroupB dispatchTouchEvent ViewGroupB onInterceptTouchEvent ViewGroupB onTouchEvent ViewGroupA onTouchEvent若View的onTouchEvent()方法返回true的分發機制流程:
ViewGroupA dispatchTouchEvent ViewGroupA onInterceptTouchEvent ViewGroupB dispatchTouchEvent ViewGroupB onInterceptTouchEvent View dispatchTouchEvent View onTouchEvent若ViewGroupB的onTouchEvent()方法返回true的分發機制流程:
ViewGroupA dispatchTouchEvent ViewGroupA onInterceptTouchEvent ViewGroupB dispatchTouchEvent ViewGroupB onInterceptTouchEvent View dispatchTouchEvent View onTouchEvent ViewGroupB onTouchEvent簡單的說dispatchTouchEvent()和onInterceptTouchEvent()是從下往上一層一層分發下去的,而onTouchEvent()是從上往下一層一層分發下去的
public class CustomTextView extends TextView { private Paint paint1, paint2; public CustomTextView(Context context, AttributeSet attrs) { super(context, attrs); initPaint(); } /** * 初始化畫筆 */ private void initPaint() { paint1 = new Paint(); paint1.setColor(getResources().getColor(android.R.color.holo_blue_light)); paint1.setStyle(Paint.Style.FILL); paint2 = new Paint(); paint2.setColor(Color.YELLOW); paint2.setStyle(Paint.Style.FILL); } @Override protected void onDraw(Canvas canvas) { //繪制外層矩形 canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), paint1); //繪制內層矩形 canvas.drawRect(10, 10, getMeasuredWidth() - 10, getMeasuredHeight() - 10, paint2); canvas.save(); //繪制文字前平移10像素 canvas.translate(10, 0); //父類完成的方法,即繪制文本 super.onDraw(canvas); canvas.restore(); } }
public class FlashTextView extends TextView { int mViewWidth = 0; private Paint mPaint; private LinearGradient mLinearGradient; private Matrix matrix; private int mTranslate; public FlashTextView(Context context, AttributeSet attrs) { super(context, attrs); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); if (mViewWidth == 0) { mViewWidth = getMeasuredWidth(); if (mViewWidth > 0) { mPaint = getPaint(); mLinearGradient = new LinearGradient(0, 0, mViewWidth, 0, new int[]{Color.BLUE, 0xffffffff, Color.BLUE}, null, Shader.TileMode.CLAMP); mPaint.setShader(mLinearGradient); matrix = new Matrix(); } } } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); if (matrix != null) { mTranslate += mViewWidth + 5; if (mTranslate > 2 * mViewWidth / 5) { mTranslate = -mViewWidth; } matrix.setTranslate(mTranslate, 0); mLinearGradient.setLocalMatrix(matrix); postInvalidateDelayed(100); } } }
在values文件夾中創建一個attrs.xml文件來自定義屬性
開始創建我們的ToolBar
public class ToolBar extends RelativeLayout { private int mLeftTextColor; private Drawable mLeftBackground; private String mLeftText; private int mRightTextColor; private Drawable mRightBackgroup; private String mRightText; private float mTitleTextSize; private int mTitleTextColor; private String mTitle; private Button mLeftButton; private Button mRightButton; private TextView mTitleView; private RelativeLayout.LayoutParams mLeftParams; private RelativeLayout.LayoutParams mRightParams; private RelativeLayout.LayoutParams mTitleParams; //帶參構造方法 public ToolBar(Context context, AttributeSet attrs) { super(context, attrs); //通過這個方法,將你在attrs.xml文件中定義的declare-styleable //的所有屬性的值存儲到TypedArray中 TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.TopBar); //從TypedArray中取出對應的值來設置的屬性賦值 mLeftTextColor = ta.getColor(R.styleable.TopBar_leftTextColor, 0); mLeftBackground = ta.getDrawable(R.styleable.TopBar_leftBackground); mLeftText = ta.getString(R.styleable.TopBar_leftText); mRightTextColor = ta.getColor(R.styleable.TopBar_rightTextColor, 0); mRightBackgroup = ta.getDrawable(R.styleable.TopBar_rightBackground); mRightText = ta.getString(R.styleable.TopBar_rightText); mTitleTextSize = ta.getDimension(R.styleable.TopBar_titleTextSize, 10); mTitleTextColor = ta.getColor(R.styleable.TopBar_titleTextColor, 0); mTitle = ta.getString(R.styleable.TopBar_title); //獲取完TypedArray的值之後,一般要調用recycle方法來避免重復創建時候的錯誤 ta.recycle(); mLeftButton = new Button(context); mRightButton = new Button(context); mTitleView = new TextView(context); //為創建的元素賦值 mLeftButton.setTextColor(mLeftTextColor); mLeftButton.setBackground(mLeftBackground); mLeftButton.setText(mLeftText); mRightButton.setTextColor(mRightTextColor); mRightButton.setBackground(mRightBackgroup); mRightButton.setText(mRightText); mTitleView.setText(mTitle); mTitleView.setTextColor(mTitleTextColor); mTitleView.setTextSize(mTitleTextSize); mTitleView.setGravity(Gravity.CENTER); //為組件元素設置相應的布局元素 mLeftParams = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT); mLeftParams.addRule(RelativeLayout.ALIGN_PARENT_LEFT); addView(mLeftButton, mLeftParams); mRightParams = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT); mRightParams.addRule(RelativeLayout.ALIGN_PARENT_RIGHT); addView(mRightButton, mRightParams); mTitleParams = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT); mTitleParams.addRule(RelativeLayout.CENTER_IN_PARENT); addView(mTitleView, mTitleParams); } }
在布局文件中使用
public class CircleProgressView extends View { private int mCircleXY; private int length; private float mRadius; private Paint mCirclePaint; private Paint mArcPaint; private Paint mTextPaint; private String mShowText = "Hensen_"; private int mTextSize = 25; private float mSweepValue = 270; public CircleProgressView(Context context, AttributeSet attrs) { super(context, attrs); //獲取屏幕高寬 WindowManager wm = (WindowManager) getContext() .getSystemService(Context.WINDOW_SERVICE); length = wm.getDefaultDisplay().getWidth(); init(); } private void init() { mCircleXY = length / 2; mRadius = (float) (length * 0.5 / 2); mCirclePaint = new Paint(); mCirclePaint.setColor(Color.BLUE); mArcPaint = new Paint(); mArcPaint.setStrokeWidth(50); mArcPaint.setStyle(Paint.Style.STROKE); mArcPaint.setColor(Color.BLUE); mTextPaint = new Paint(); mTextPaint.setColor(Color.WHITE); mTextPaint.setTextSize(mTextSize); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); //矩形 RectF mArcRectF = new RectF((float) (length * 0.1), (float) (length * 0.1), (float) (length * 0.9), (float) (length * 0.9)); //繪制圓 canvas.drawCircle(mCircleXY, mCircleXY, mRadius, mCirclePaint); //繪制弧線 canvas.drawArc(mArcRectF, 270, mSweepValue, false, mArcPaint); //繪制文字 canvas.drawText(mShowText, 0, mShowText.length(), mCircleXY, mCircleXY + (mTextSize / 4), mTextPaint); } public void setSweepValue(float sweepValue) { if (sweepValue != 0) { mSweepValue = sweepValue; } else { mSweepValue = 25; } invalidate(); } }
當用戶不指定具體的比例值時,可以調用以下代碼來設置相應的比例值
CircleProgressView circleProgressView = (CircleProgressView) findViewById(R.id.circle); circleProgressView.setSweepValue(270);
public class MusicView extends View { private int mWidth; private int mRectHeight; private int mRectWidth; private int mRectCount = 20; private LinearGradient mLinearGradient; private Paint mPaint=new Paint(); private float currentHeight; private int offset = 5; private double mRandom; public MusicView(Context context, AttributeSet attrs) { super(context, attrs); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); mWidth = getWidth(); mRectHeight = getHeight(); mRectWidth = (int) (mWidth * 0.6 / mRectCount); mLinearGradient = new LinearGradient(0, 0, mRectWidth, mRectHeight, Color.YELLOW, Color.BLUE, Shader.TileMode.CLAMP); mPaint.setShader(mLinearGradient); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); //遍歷繪制矩形,留中間間隔 for (int i = 0; i < mRectCount; i++) { //開始繪制 canvas.drawRect((float) (mWidth * 0.4 / 2 + mRectWidth * i + offset), currentHeight, (float) (mWidth * 0.4 / 2 + mRectWidth * (i + 1)), mRectHeight, mPaint); } //獲取隨機數 mRandom = Math.random(); currentHeight = ((float) (mRectHeight * mRandom)); //延遲300去刷新 postInvalidateDelayed(300); } }
自定義的ScrollView沒有系統自帶的性能好,畢竟很多因素都沒考慮到,這裡只是適用於練手使用
public class CustomScrollView extends ViewGroup { private int mScreenHeight; private Scroller mScroller; private int mLastY; private int mStart; private int mEnd; public CustomScrollView(Context context, AttributeSet attrs) { super(context, attrs); //獲取屏幕高寬 WindowManager wm = (WindowManager) getContext() .getSystemService(Context.WINDOW_SERVICE); mScreenHeight = wm.getDefaultDisplay().getHeight(); mScroller = new Scroller(getContext()); } @Override protected void onLayout(boolean b, int i, int i1, int i2, int i3) { int childCount = getChildCount(); MarginLayoutParams mlp = (MarginLayoutParams) getLayoutParams(); mlp.height = mScreenHeight * childCount; setLayoutParams(mlp); for (int j = 0; j < childCount; j++) { View child = getChildAt(j); if (child.getVisibility() != View.GONE) { child.layout(i, j * mScreenHeight, i2, (j + 1) * mScreenHeight); } } } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); int count = getChildCount(); for (int i = 0; i < count; ++i) { View childView = getChildAt(i); measureChild(childView, widthMeasureSpec, heightMeasureSpec); } } @Override public boolean onTouchEvent(MotionEvent event) { int y = (int) event.getY(); switch (event.getAction()) { case MotionEvent.ACTION_DOWN: mLastY = y; mStart = getScrollY(); break; case MotionEvent.ACTION_MOVE: if (!mScroller.isFinished()) { mScroller.abortAnimation(); } int dy = mLastY - y; if (getScrollY() < 0) { dy = 0; } if (getScrollY() > getHeight() - mScreenHeight) { dy = 0; } scrollBy(0, dy); mLastY = y; break; case MotionEvent.ACTION_UP: mEnd = getScrollY(); int dScrollY = mEnd - mStart; if (dScrollY > 0) { if (dScrollY < mScreenHeight / 3) { mScroller.startScroll(0, getScrollY(), 0, -dScrollY); } else { mScroller.startScroll(0, getScrollY(), 0, mScreenHeight - dScrollY); } } else { if (-dScrollY < mScreenHeight / 3) { mScroller.startScroll(0, getScrollY(), 0, -dScrollY); } else { mScroller.startScroll(0, getScrollY(), 0, -mScreenHeight - dScrollY); } } break; } postInvalidate(); return true; } @Override public void computeScroll() { super.computeScroll(); if (mScroller.computeScrollOffset()) { scrollTo(0, mScroller.getCurrY()); } } }
在布局中使用
經典回顧源碼下載
github:https://github.com/CSDNHensen/QunYingZhuang
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