viewgroup简单说就是可以装view的view.今天遇到一个问题,就是需要一个可以自动根据一行中view的宽度自动换行的布局,网上找了下,没有相关的例子,但是找到了思路:自定义一个viewgroup,然后在onlayout文件里面自动检测view的右边缘的横坐标值,和你的view的parent view的况度判断是否换行显示view就可以了。因为代码比较简单,就不多说了:
1 public class MyViewGroup extends ViewGroup { 2 private final static String TAG = "123"; 3 4 private final static int VIEW_MARGIN=2; 5 6 public MyViewGroup(Context context, AttributeSet attrs){ 7 super(context, attrs); 8 } 9 10 public MyViewGroup(Context context) { 11 super(context); 12 } 13 @Override 14 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 15 Log.d(TAG, "widthMeasureSpec = "+widthMeasureSpec+" heightMeasureSpec = "+heightMeasureSpec); 16 17 for (int index = 0; index < getChildCount(); index++) { 18 final View child = getChildAt(index); 19 // measure 20 child.measure(MeasureSpec.UNSPECIFIED, MeasureSpec.UNSPECIFIED); 21 } 22 23 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 24 } 25 private int jiange = 10;//按钮之间的间隔 26 @Override 27 protected void onLayout(boolean arg0, int arg1, int arg2, int arg3, int arg4) { 28 Log.d(TAG, "changed = "+arg0+" left = "+arg1+" top = "+arg2+" right = "+arg3+" botom = "+arg4); 29 final int count = getChildCount(); 30 int row=0;// which row lay you view relative to parent 31 int lengthX=arg1 ; // right position of child relative to parent 32 int lengthY=arg2; // bottom position of child relative to parent 33 for(int i=0;i<count;i++){ 34 35 final View child = this.getChildAt(i); 36 int width = child.getMeasuredWidth(); 37 int height = child.getMeasuredHeight(); 38 if(i == 0){ 39 lengthX+=width+VIEW_MARGIN;//第一个的时候不需要加 40 }else{ 41 lengthX+=width+VIEW_MARGIN +jiange;//按钮之间的间隔 42 } 43 lengthY=row*(height+VIEW_MARGIN)+VIEW_MARGIN+height+arg2; 44 //if it can't drawing on a same line , skip to next line 45 if(lengthX>arg3){ 46 lengthX=width+VIEW_MARGIN+arg1; 47 row++; 48 lengthY=row*(height+VIEW_MARGIN)+VIEW_MARGIN+height+arg2; 49 } 50 child.layout(lengthX-width, lengthY-height, lengthX, lengthY); 51 } 52 } 53 }
这里有个地方要注意,那就要明白ViewGroup的绘图流程:ViewGroup绘制包括两个步骤:1.measure 2.layout
在两个步骤中分别调用回调函数:1.onMeasure() 2.onLayout()
1.onMeasure() 在这个函数中,ViewGroup会接受childView的请求的大小,然后通过childView的 measure(newWidthMeasureSpec, heightMeasureSpec)函数存储到childView中,以便childView的getMeasuredWidth() andgetMeasuredHeight() 的值可以被后续工作得到。
2.onLayout() 在这个函数中,ViewGroup会拿到childView的getMeasuredWidth() andgetMeasuredHeight(),用来布局所有的childView。
3.View.MeasureSpec 与 LayoutParams 这两个类,是ViewGroup与childView协商大小用的。其中,View.MeasureSpec是ViewGroup用来部署 childView用的, LayoutParams是childView告诉ViewGroup 我需要多大的地方。
4.在View 的onMeasure的最后要调用setMeasuredDimension()这个方法存储View的大小,这个方法决定了当前View的大小。
Activity code:
1 public class GooleActivity extends Activity { 2 @Override 3 public void onCreate(Bundle savedInstanceState) { 4 super.onCreate(savedInstanceState); 5 setContentView(R.layout.main); 6 MyViewGroup myViewGroup = (MyViewGroup) this.findViewById(R.id.myviewgroup); 7 for(int i = 0 ; i<15;i++){ 8 Button button = null; 9 if(i%2==0){ 10 button = new Button(this); 11 button.setText("偶数"+i); 12 }else if(i%3==0){ 13 button = new Button(this); 14 button.setText("奇数奇数奇数奇数"+i); 15 }else{ 16 button = new Button(this); 17 button.setText("超长的超长的超长的"+i); 18 } 19 20 myViewGroup.addView(button); 21 } 22 } 23 }
xml code:
1 <?xml version="1.0" encoding="utf-8"?> 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 3 android:layout_width="fill_parent" 4 android:layout_height="fill_parent" 5 android:orientation="vertical" > 6 7 <com.xy.activity.MyViewGroup 8 android:id="@+id/myviewgroup" 9 android:layout_width="fill_parent" 10 android:layout_height="fill_parent" /> 11 12 </LinearLayout>
效果图: