Android群英传知识点回顾——第三章:Android控件架构与自定义控件详解
2016-10-08 15:01
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Android群英传知识点回顾——第三章:Android控件架构与自定义控件详解
知识点目录
3.1 Android控件架构3.2 View的测量
3.3 View的绘制
3.4 ViewGroup的测量
3.5 ViewGroup的绘制
3.6 自定义View
3.6.1 对现有的空间进行拓展
3.6.2 创建复合控件
3.6.3 重写View来实现全新的空间
3.7 自定义ViewGroup
3.8 事件拦截机制分析
知识点回顾
3.1 Android控件架构
控件大致非为两类:view控件:视图控件
viewGroup控件:包含多个View控件,并管理其包含的View控件
两者之间的关系:上层控件负责下层子控件的测量与绘制,并传递交互事件
UI界面架构:
Activity都包含一个Window对象,通常由PhoneWindow来实现
PhoneWindow将一个DecorView设置为整个应用窗口的根View
DecorView为整个Window界面的最顶层View
DecorView只有一个子元素为LinearLayout,代表整个Window界面,包含通知栏,标题栏,内容显示栏三块区域
LinearLayout里有两个FrameLayout子元素:
标题栏显示界面。只有一个TextView显示应用的名称
内容栏显示界面。就是setContentView()方法载入的布局界面
3.2 View的测量
MeasureSpec类:32位的int值,高2位为测量模式,低30位为测量大小MeasureSpec模式:
EXACTLY:精确模式 ,当控件的layout_width属性或layout_height属性指定为具体值,控件大小也是该具体值
AT_MOST:最大值模式,当控件layout_width属性或layout_height属性指定为warp_content时,控件的尺寸不要超过父控件允许的最大尺寸
UNSPECIFIED:未指定模式,控件要多大就多大,通常情况下再绘制自定义View中才会使用
View类默认的onMeasure()方法只支持EXACTLY模式,View需要支持warp_content属性,那么就必须重写onMeasure()方法,来制定warp_content的大小
下面我们通过一个简单的实例,演示如何进行View的测量,首先,需要重写onMeasure()方法:
@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); }
可以发现,onMeasure方法调用了父类的onMeasure方法,代码跟踪父类onMeasure方法
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec), getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec)); }
可以发现,系统最终会调用setMeasuredDimension(int measuredWidth,int measuredHeight)方法将测量后的宽高值设置进去,我们调用自定义的measureWidth()方法和measureHeight()方法,分别对宽高进行重新定义
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { setMeasuredDimension(measureWidth(widthMeasureSpec),measureHeight(heightMeasureSpec)); }
下面以measureWidth()方法为例:
第一步:从MeasureSpec对象中提取出具体的测量模式和大小
int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec);
第二步:通过不同的测量模式给出不同的测量值:
EXACTLY:使用指定的specSize即可
AT_MOST:取出我们指定的大小和SpecSize的最小值
UNSPECIFIED:200px
下面这段代码基本上可以作为模板代码:
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;
}
可以发现,当指定warp_content属性时,View就获得一个默认值200px
3.3 View的绘制
当测量好了一个View之后,我们通过重写View类中的onDraw()方法来绘图,要想绘制相应的图像,就必须在Canvas上进行绘制Canvas canvas = new Canvas(Bitmap);
Canvas就像是一个画板,我们传进去一个bitmap,通过这个bitmap创建的Canvas画布紧紧联系在一起,这个过程我们称之为装载画布,这个bitmap用来存储所有绘制在Canvas上的像素信息,所以当你在后面调用所有的Canvas.drawxxx方法都会发生在这个bitmap上
3.4 ViewGroup的测量
ViewGroup在测量时通过遍历所有子View,从而调用子View的Measure方法来获得每一个子View的结果@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测量完毕后,通常会去重写onLayout()方法来控制其子View显示位置的逻辑
@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); } }
3.5 ViewGroup的绘制
ViewGroup通常不需要绘制,如果不是指定ViewGroup的背景颜色,那么ViewGroup的onDraw()方法都不会被调用,但是,ViewGroup会使用dispatchDraw()方法来绘制子View@Override protected void dispatchDraw(Canvas canvas) { super.dispatchDraw(canvas); }
3.6 自定义View
在View中通常有以下一些重要的回调方法:onFinishInflate():从XML加载组件后回调
onSizeChanged():组件大小改变时回调
onMeasure():回调该方法来进行测量
onLayout():回调该方法来确定显示的位置
onTouchEvent():监听到触摸事件时回调
通常情况下,有以下三种方法来实现自定义的控件:
对现有的控件进行拓展
通过组合来实现新的控件
重写View来实现全新的控件
3.6.1 对现有的控件进行拓展
自定义修改TextView……见经典代码回顾,案例一
闪动的文字效果……见经典代码回顾,案例二
3.6.2 创建复合控件
自定义ToolBar的实现……见经典代码回顾,案例三
3.6.3 重写View来实现全新的控件
弧线展示图……见经典代码回顾,案例四
音频条形图……见经典代码回顾,案例五
3.7 自定义ViewGroup
自定义ViewGroup,仿ScrollView……见经典代码回顾,案例六3.8 事件拦截机制分析
事件拦截机制三个重要方法dispatchTouchEvent():分发事件
onInterceptTouchEvent():拦截事件
onTouchEvent():处理事件
举一个例子说明事件分发机制:
ViewGroupA:处于视图最下层
ViewGroupB:处于视图中间层
View:处于视图最上层
正常的事件分发机制流程:
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的分发机制流程:
ViewGroupA dispatchTouchEvent
ViewGroupA onInterceptTouchEvent
ViewGroupB dispatchTouchEvent
ViewGroupB onInterceptTouchEvent
ViewGroupB onTouchEvent
ViewGroupA onTouchEvent
若View的onTouchEvent()方法返回true的分发机制流程:
ViewGroupA dispatchTouchEvent
ViewGroupA onInterceptTouchEvent
ViewGroupB dispatchTouchEvent
ViewGroupB onInterceptTouchEvent
View dispatchTouchEvent
View onTouchEvent
若ViewGroupB的onTouchEvent()方法返回true的分发机制流程:
ViewGroupA dispatchTouchEvent
ViewGroupA onInterceptTouchEvent
ViewGroupB dispatchTouchEvent
ViewGroupB onInterceptTouchEvent
View dispatchTouchEvent
View onTouchEvent
ViewGroupB onTouchEvent
简单的说dispatchTouchEvent()和onInterceptTouchEvent()是从下往上一层一层分发下去的,而onTouchEvent()是从上往下一层一层分发下去的
经典代码回顾
案例一:自定义修改TextView
public class CustomTextView extends TextView { private Paint paint1, paint2; public CustomTextView(Context context, AttributeSet attrs) { super(context, attrs); initPaint(); } /** * 初始化画笔 */ 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) { //绘制外层矩形 canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), paint1); //绘制内层矩形 canvas.drawRect(10, 10, getMeasuredWidth() - 10, getMeasuredHeight() - 10, paint2); canvas.save(); //绘制文字前平移10像素 canvas.translate(10, 0); //父类完成的方法,即绘制文本 super.onDraw(canvas); canvas.restore(); } }
效果图
案例二:闪动的文字效果
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); } } }
效果图
案例三:自定义ToolBar的实现
在values文件夹中创建一个attrs.xml文件来自定义属性<?xml version="1.0" encoding="utf-8"?> <resources> <declare-styleable name="TopBar"> <attr name="title" format="string" /> <attr name="titleTextSize" format="dimension" /> <attr name="titleTextColor" format="color" /> <attr name="leftTextColor" format="color" /> <attr name="leftBackground" format="reference|color" /> <attr name="leftText" format="string" /> <attr name="rightTextColor" format="color" /> <attr name="rightBackground" format="reference|color" /> <attr name="rightText" format="string" /> </declare-styleable> </resources>
开始创建我们的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; //带参构造方法 public ToolBar(Context context, AttributeSet attrs) { super(context, attrs); //通过这个方法,将你在attrs.xml文件中定义的declare-styleable //的所有属性的值存储到TypedArray中 TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.TopBar); //从TypedArray中取出对应的值来设置的属性赋值 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); //获取完TypedArray的值之后,一般要调用recycle方法来避免重复创建时候的错误 ta.recycle(); mLeftButton = new Button(context); mRightButton = new Button(context); mTitleView = new TextView(context); //为创建的元素赋值 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); //为组件元素设置相应的布局元素 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
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent"> <com.handsome.qunyingzhuang.chapter_3.ToolBar.ToolBar xmlns:custom="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="40dp" custom:leftBackground="#0000ff" custom:leftText="back" custom:leftTextColor="#00ff00" custom:rightBackground="#333333" custom:rightText="more" custom:rightTextColor="#ff0000" custom:title="我的标题" custom:titleTextColor="#ff0000" custom:titleTextSize="14sp" /> </RelativeLayout>
效果图
案例四:弧线展示图
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); //获取屏幕高宽 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)); //绘制圆 canvas.drawCircle(mCircleXY, mCircleXY, mRadius, mCirclePaint); //绘制弧线 canvas.drawArc(mArcRectF, 270, mSweepValue, false, mArcPaint); //绘制文字 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(); } }
当用户不指定具体的比例值时,可以调用以下代码来设置相应的比例值
CircleProgressView circleProgressView = (CircleProgressView) findViewById(R.id.circle); circleProgressView.setSweepValue(270);
效果图
案例五:音频条形图
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); //遍历绘制矩形,留中间间隔 for (int i = 0; i < mRectCount; i++) { //开始绘制 canvas.drawRect((float) (mWidth * 0.4 / 2 + mRectWidth * i + offset), currentHeight, (float) (mWidth * 0.4 / 2 + mRectWidth * (i + 1)), mRectHeight, mPaint); } //获取随机数 mRandom = Math.random(); currentHeight = ((float) (mRectHeight * mRandom)); //延迟300去刷新 postInvalidateDelayed(300); } }
效果图
案例六:自定义ViewGroup,仿ScrollView
自定义的ScrollView没有系统自带的性能好,毕竟很多因素都没考虑到,这里只是适用于练手使用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); //获取屏幕高宽 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
<?xml version="1.0" encoding="utf-8"?> <com.handsome.qunyingzhuang.chapter_3.CustomScrollView.CustomScrollView xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent"> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:background="#ff0000" android:text="Hensen_博客(1)" /> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:background="#00ff00" android:text="Hensen_博客(2)" /> </com.handsome.qunyingzhuang.chapter_3.CustomScrollView.CustomScrollView>
效果图
经典回顾源码下载
github:https://github.com/CSDNHensen/QunYingZhuang
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