Android中View绘制流程以及invalidate()等相关方法分析(3)_H5之家

1、 MyViewGroup.java 自定义ViewGroup类型

/** * @author ://blog.csdn.net/qinjuning */ //自定义ViewGroup 对象 public class MyViewGroup extends ViewGroup{ private static String TAG = "MyViewGroup" ; private Context mContext ; public MyViewGroup(Context context) { super(context); mContext = context ; init() ; } //xml定义的属性,需要该构造函数 public MyViewGroup(Context context , AttributeSet attrs){ super(context,attrs) ; mContext = context ; init() ; } //为MyViewGroup添加三个子View private void init(){ //调用ViewGroup父类addView()方法添加子View //child 对象一： Button Button btn= new Button(mContext) ; btn.setText("I am Button") ; this.addView(btn) ; //child 对象二 : ImageView ImageView img = new ImageView(mContext) ; img.setBackgroundResource(R.drawable.icon) ; this.addView(img) ; //child 对象三 : TextView TextView txt = new TextView(mContext) ; txt.setText("Only Text") ; this.addView(txt) ; //child 对象四：自定义View MyView myView = new MyView(mContext) ; this.addView(myView) ; } @Override //对每个子View进行measure():设置每子View的大小，即实际宽和高 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){ //通过init()方法，我们为该ViewGroup对象添加了三个视图， Button、 ImageView、TextView int childCount = getChildCount() ; Log.i(TAG, "the size of this ViewGroup is ----> " + childCount) ; Log.i(TAG, "**** onMeasure start *****") ; //获取该ViewGroup的实际长和宽涉及到MeasureSpec类的使用 int specSize_Widht = MeasureSpec.getSize(widthMeasureSpec) ; int specSize_Heigth = MeasureSpec.getSize(heightMeasureSpec) ; Log.i(TAG, "**** specSize_Widht " + specSize_Widht+ " * specSize_Heigth *****" + specSize_Heigth) ; //设置本ViewGroup的宽高 setMeasuredDimension(specSize_Widht , specSize_Heigth) ; for(int i=0 ;i<childCount ; i++){ View child = getChildAt(i) ; //获得每个对象的引用 child.measure(50, 50) ; //简单的设置每个子View对象的宽高为 50px , 50px //或者可以调用ViewGroup父类方法measureChild()或者measureChildWithMargins()方法 //this.measureChild(child, widthMeasureSpec, heightMeasureSpec) ; } } @Override //对每个子View视图进行布局 protected void onLayout(boolean changed, int l, int t, int r, int b) { // TODO Auto-generated method stub //通过init()方法，我们为该ViewGroup对象添加了三个视图， Button、 ImageView、TextView int childCount = getChildCount() ; int startLeft = 0 ;//设置每个子View的起始横坐标 int startTop = 10 ; //每个子View距离父视图的位置，简单设置为10px吧。可以理解为 android:margin=10px ; Log.i(TAG, "**** onLayout start ****") ; for(int i=0 ;i<childCount ; i++){ View child = getChildAt(i) ; //获得每个对象的引用 child.layout(startLeft, startTop, startLeft+child.getMeasuredWidth(), startTop+child.getMeasuredHeight()) ; startLeft =startLeft+child.getMeasuredWidth() + 10; //校准startLeft值，View之间的间距设为10px ; Log.i(TAG, "**** onLayout startLeft ****" +startLeft) ; } } //绘图过程Android已经为我们封装好了 ,这儿只为了观察方法调用程 protected void dispatchDraw(Canvas canvas){ Log.i(TAG, "**** dispatchDraw start ****") ; super.dispatchDraw(canvas) ; } protected boolean drawChild(Canvas canvas , View child, long drawingTime){ Log.i(TAG, "**** drawChild start ****") ; return super.drawChild(canvas, child, drawingTime) ; } }

2、MyView.java 自定义View类型，重写onDraw()方法，

//自定义View对象 public class MyView extends View{ private Paint paint = new Paint() ; public MyView(Context context) { super(context); // TODO Auto-generated constructor stub } public MyView(Context context , AttributeSet attrs){ super(context,attrs); } protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){ //设置该View大小为 80 80 setMeasuredDimension(50 , 50) ; } //存在canvas对象，即存在默认的显示区域 @Override public void onDraw(Canvas canvas) { // TODO Auto-generated method stub super.onDraw(canvas); Log.i("MyViewGroup", "MyView is onDraw ") ; //加粗 paint.setTypeface(Typeface.defaultFromStyle(Typeface.BOLD)); paint.setColor(Color.RED); canvas.drawColor(Color.BLUE) ; canvas.drawRect(0, 0, 30, 30, paint); canvas.drawText("MyView", 10, 40, paint); } }

View绘制过程中如何绘制背景图片：

//==========================================================

// 本次更新于 2012-10-29 晚

//==========================================================