自定义View和ViewGroup常用方法执行顺序

1. 自定义View常用方法执行顺序

1.创建MyView继承View

public class MyView extends View {    public MyView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);        Log.d("MyView", "MyView(2): ");    }    @Override    protected void onFinishInflate() {        Log.d("MyView", "onFinishInflate: ");        super.onFinishInflate();    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        Log.d("MyView", "onMeasure: ");        super.onMeasure(widthMeasureSpec, heightMeasureSpec);    }    @Override    protected void onDraw(Canvas canvas) {        Log.d("MyView", "onDraw: ");        super.onDraw(canvas);    }    @Override    protected void dispatchDraw(Canvas canvas) {        Log.d("MyView", "dispatchDraw: ");        super.dispatchDraw(canvas);    }    @Override    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {        Log.d("MyView", "onLayout: ");        super.onLayout(changed, left, top, right, bottom);    }    @Override    protected void onSizeChanged(int w, int h, int oldw, int oldh) {        Log.d("MyView", "onSizeChanged: ");        super.onSizeChanged(w, h, oldw, oldh);    }    @Override    protected void onAttachedToWindow() {        Log.d("MyView", "onAttachedToWindow: ");        super.onAttachedToWindow();    }    @Override    public void onWindowFocusChanged(boolean hasWindowFocus) {        Log.d("MyView", "onWindowFocusChanged: ");        super.onWindowFocusChanged(hasWindowFocus);    }}

2.xml文件中使用

<com.wgheng.test.MyView xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="100dp"    android:layout_height="100dp"></com.wgheng.test.MyViewGroup>

3.Log输出情况

 06-30 08:19:44.487 11310-11310/com.wgheng.text D/MyView: MyView(2):  06-30 08:19:44.487 11310-11310/com.wgheng.text D/MyView: onFinishInflate:  06-30 08:19:44.540 11310-11310/com.wgheng.text D/MyView: onAttachedToWindow:  06-30 08:19:44.553 11310-11310/com.wgheng.text D/MyView: onMeasure:  06-30 08:19:44.673 11310-11310/com.wgheng.text D/MyView: onMeasure:  06-30 08:19:44.673 11310-11310/com.wgheng.text D/MyView: onSizeChanged:  06-30 08:19:44.673 11310-11310/com.wgheng.text D/MyView: onLayout:  06-30 08:19:44.704 11310-11310/com.wgheng.text D/MyView: onWindowFocusChanged:  06-30 08:19:44.706 11310-11310/com.wgheng.text D/MyView: onMeasure:  06-30 08:19:44.706 11310-11310/com.wgheng.text D/MyView: onLayout:  06-30 08:19:44.707 11310-11310/com.wgheng.text D/MyView: onDraw:  06-30 08:19:44.707 11310-11310/com.wgheng.text D/MyView: dispatchDraw:

从日志中可以看到onWindowFocusChanged()执行时View已经完成了初步的Layout。

Activity生命周期执行的过程中获得或失去焦点时会回调同名的方法，在此同名方法中又回调了View的onWindowFocusChanged()方法，因此比较适合在Activity的onWindowFocusChanged()方法中获取视图的宽和高。

如果在Activity其他方法中获取View的宽和高，很有可能View还未初始化完毕，获得的值为0。

2. 自定义ViewGroup常用方法执行顺序

1.自定义MyViewGroup继承ViewGroup（简单起见继承LinearLayout测试）

public class MyViewGroup extends LinearLayout {    public MyViewGroup(Context context, AttributeSet attrs) {        super(context, attrs);        Log.d("MyViewGroup", "MyViewGroup(2): ");    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        Log.d("MyViewGroup", "onMeasure: ");        super.onMeasure(widthMeasureSpec, heightMeasureSpec);    }    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {        Log.d("MyViewGroup", "onLayout: ");        super.onLayout(changed, l, t, r, b);    }     @Override    protected void onSizeChanged(int w, int h, int oldw, int oldh) {        Log.d("MyViewGroup", "onSizeChanged: ");        super.onSizeChanged(w, h, oldw, oldh);    }    @Override    protected void onDraw(Canvas canvas) {        Log.d("MyViewGroup", "onDraw: ");        super.onDraw(canvas);    }    @Override    protected void dispatchDraw(Canvas canvas) {        Log.d("MyViewGroup", "dispatchDraw: ");        super.dispatchDraw(canvas);    }    @Override    protected void onFinishInflate() {        Log.d("MyViewGroup", "onFinishInflate: ");        super.onFinishInflate();    }    @Override    protected void onAttachedToWindow() {        Log.d("MyViewGroup", "onAttachedToWindow: ");        super.onAttachedToWindow();    }    @Override    public void onWindowFocusChanged(boolean hasWindowFocus) {        Log.d("MyViewGroup", "onWindowFocusChanged: ");        super.onWindowFocusChanged(hasWindowFocus);    }}

2.xml文件中使用

1> 未设置背景

<com.wgheng.test.MyViewGroup xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="100dp"    android:layout_height="100dp"></com.wgheng.test.MyViewGroup>

1> 设置背景

<com.wgheng.test.MyViewGroup xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="100dp"    android:layout_height="100dp"    android:background="#000000"></com.wgheng.test.MyViewGroup>

3.Log输出情况

1> 未设置背景输出情况

06-30 08:20:52.594 12349-12349/com.wgheng.text D/MyViewGroup: MyViewGroup(2): 06-30 08:20:52.594 12349-12349/com.wgheng.text D/MyViewGroup: onFinishInflate: 06-30 08:20:52.639 12349-12349/com.wgheng.text D/MyViewGroup: onAttachedToWindow: 06-30 08:20:52.644 12349-12349/com.wgheng.text D/MyViewGroup: onMeasure: 06-30 08:20:52.736 12349-12349/com.wgheng.text D/MyViewGroup: onMeasure: 06-30 08:20:52.736 12349-12349/com.wgheng.text D/MyViewGroup: onSizeChanged: 06-30 08:20:52.738 12349-12349/com.wgheng.text D/MyViewGroup: onLayout: 06-30 08:20:52.763 12349-12349/com.wgheng.text D/MyViewGroup: onWindowFocusChanged: 06-30 08:20:52.765 12349-12349/com.wgheng.text D/MyViewGroup: onMeasure: 06-30 08:20:52.765 12349-12349/com.wgheng.text D/MyViewGroup: onLayout: 06-30 08:20:52.766 12349-12349/com.wgheng.text D/MyViewGroup: dispatchDraw: 

2> 设置背景输出情况

06-30 08:30:51.470 21347-21347/com.wgheng.test D/MyViewGroup: MyViewGroup(2): 06-30 08:30:51.470 21347-21347/com.wgheng.test D/MyViewGroup: onFinishInflate: 06-30 08:30:51.541 21347-21347/com.wgheng.test D/MyViewGroup: onAttachedToWindow: 06-30 08:30:51.557 21347-21347/com.wgheng.test D/MyViewGroup: onMeasure: 06-30 08:30:51.675 21347-21347/com.wgheng.test D/MyViewGroup: onMeasure: 06-30 08:30:51.675 21347-21347/com.wgheng.test D/MyViewGroup: onSizeChanged: 06-30 08:30:51.675 21347-21347/com.wgheng.test D/MyViewGroup: onLayout: 06-30 08:30:51.776 21347-21347/com.wgheng.test D/MyViewGroup: onWindowFocusChanged: 06-30 08:30:51.779 21347-21347/com.wgheng.test D/MyViewGroup: onMeasure: 06-30 08:30:51.779 21347-21347/com.wgheng.test D/MyViewGroup: onLayout: 06-30 08:30:51.779 21347-21347/com.wgheng.test D/MyViewGroup: onDraw: //绘制背景时回调了onDraw()06-30 08:30:51.779 21347-21347/com.wgheng.test D/MyViewGroup: dispatchDraw: 

Log中可以看到ViewGroup方法执行顺序和View唯一的差别在于，当ViewGroup绘制背景时会调用onDraw()方法，不绘制背景时就跳过onDraw()方法，执行dispatchDraw()方法

3. ViewGroup嵌套View时方法的执行顺序

1.xml文件中使用

<com.wgheng.test.MyViewGroup xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="100dp"    android:layout_height="100dp"    android:background="#000000">    <com.wgheng.test.MyView        android:layout_width="100dp"        android:layout_height="100dp" /></com.wgheng.test.MyViewGroup>

2.Log输出情况

06-30 10:20:16.872 8869-8869/com.wgheng.test D/MyViewGroup: MyViewGroup(2): 06-30 10:20:16.888 8869-8869/com.wgheng.test D/MyView: MyView(2): 06-30 10:20:16.890 8869-8869/com.wgheng.test D/MyView: onFinishInflate: 06-30 10:20:16.890 8869-8869/com.wgheng.test D/MyViewGroup: onFinishInflate: 06-30 10:20:16.973 8869-8869/com.wgheng.test D/MyViewGroup: onAttachedToWindow: 06-30 10:20:16.973 8869-8869/com.wgheng.test D/MyView: onAttachedToWindow: 06-30 10:20:16.976 8869-8869/com.wgheng.test D/MyViewGroup: onMeasure: 06-30 10:20:16.976 8869-8869/com.wgheng.test D/MyView: onMeasure: 06-30 10:20:17.078 8869-8869/com.wgheng.test D/MyViewGroup: onMeasure: 06-30 10:20:17.078 8869-8869/com.wgheng.test D/MyView: onMeasure: 06-30 10:20:17.078 8869-8869/com.wgheng.test D/MyViewGroup: onSizeChanged: 06-30 10:20:17.078 8869-8869/com.wgheng.test D/MyViewGroup: onLayout: 06-30 10:20:17.078 8869-8869/com.wgheng.test D/MyView: onSizeChanged: 06-30 10:20:17.078 8869-8869/com.wgheng.test D/MyView: onLayout: 06-30 10:20:17.103 8869-8869/com.wgheng.test D/MyViewGroup: onWindowFocusChanged: 06-30 10:20:17.103 8869-8869/com.wgheng.test D/MyView: onWindowFocusChanged: 06-30 10:20:17.107 8869-8869/com.wgheng.test D/MyViewGroup: onMeasure: 06-30 10:20:17.107 8869-8869/com.wgheng.test D/MyView: onMeasure: 06-30 10:20:17.107 8869-8869/com.wgheng.test D/MyViewGroup: onLayout: 06-30 10:20:17.107 8869-8869/com.wgheng.test D/MyView: onLayout: 06-30 10:20:17.108 8869-8869/com.wgheng.test D/MyViewGroup: onDraw:  //仅当ViewGroup绘制背景时才执行06-30 10:20:17.108 8869-8869/com.wgheng.test D/MyViewGroup: dispatchDraw: 06-30 10:20:17.108 8869-8869/com.wgheng.test D/MyView: onDraw: 06-30 10:20:17.108 8869-8869/com.wgheng.test D/MyView: dispatchDraw: 

这个…看起来略乱，哈哈，就不总结了！