关于View和ViewGroup的拓展

1.View.AccessibilityDelegate 用来拓展View的访问性支持，常用来做埋点等操作

/**
 * 为每个View设置AccessibilityDelegate，监听各种事件
 */
public class AutoTrackActivity extends AppCompatActivity {
    @Override
    public Object getSystemService(@NonNull String name) {
        Object object = super.getSystemService(name);
        if (traceEnable() && object instanceof LayoutInflater) {
            return new TrackLayoutInflater((LayoutInflater) object, this);
        }
        return object;
    }
    public boolean traceEnable() {
        return true;
    }
    public static class TrackLayoutInflater extends LayoutInflater {
        private final LayoutInflater mProxy;
        public TrackLayoutInflater(LayoutInflater proxy, Context context) {
            super(proxy, context);
            this.mProxy = proxy;
        }
        @Override
        public LayoutInflater cloneInContext(Context newContext) {
            return new TrackLayoutInflater(mProxy, newContext);
        }
        @Override
        public View inflate(int resource, @Nullable ViewGroup root) {
            View view = mProxy.inflate(resource, root);
            View content = view.findViewById(android.R.id.content);
            if (content instanceof ViewGroup) {
                flatViews((ViewGroup) content);
            }
            return view;
        }
        private static void bindAccessibilityDelegate(View view) {
            if (view != null) {
                view.setAccessibilityDelegate(AccessibilityDelegateWrapper.create(view, new View.AccessibilityDelegate() {
                    @Override
                    public void sendAccessibilityEvent(View host, int eventType) {
                        if (eventType == AccessibilityEvent.TYPE_VIEW_CLICKED) {
                            Log.i("csz", host.getClass().getCanonicalName() + "  click");
                        }else if (eventType == AccessibilityEvent.TYPE_VIEW_LONG_CLICKED){
                            Log.i("csz", host.getClass().getCanonicalName() + "  longClick");
                        }
                        super.sendAccessibilityEvent(host, eventType);
                    }
                }));
            }
        }
        private void flatViews(ViewGroup group) {
            for (int i = 0; i < group.getChildCount(); i++) {
                View child = group.getChildAt(i);
                bindAccessibilityDelegate(child);
                if (child instanceof ViewGroup){
                    flatViews((ViewGroup) child);
                }
            }
        }
    }
}

2.View.BaseSavedState 做状态保存

static class SavedState extends BaseSavedState {
        float progress;
        SavedState(Parcelable superState) {
            super(superState);
        }
        private SavedState(Parcel in) {
            super(in);
            progress = (Float) in.readFloat();
        }
        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            out.writeValue(progress);
        }
        @Override
        public String toString() {
            return " p =" + progress + "}";
        }
        public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {
            @Override
            public SavedState createFromParcel(Parcel in) {
                return new SavedState(in);
            }
            @Override
            public SavedState[] newArray(int size) {
                return new SavedState[size];
            }
        };
    }
    @Override
    public Parcelable onSaveInstanceState() {
        Parcelable superState = super.onSaveInstanceState();
        SavedState ss = new SavedState(superState);
        ss.progress = mProgress;
        return ss;
    }
    @Override
    public void onRestoreInstanceState(Parcelable state) {
        SavedState ss = (SavedState) state;
        super.onRestoreInstanceState(ss.getSuperState());
        setProgress(ss.progress);
        requestLayout();
    }

3.View.DragShadowBuilder 构建拖动阴影

private void drag() {
        btn.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View v) {
                v.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS, HapticFeedbackConstants.FLAG_IGNORE_GLOBAL_SETTING);
                View.DragShadowBuilder builder = new View.DragShadowBuilder(v);
                ClipData data = ClipData.newPlainText("label", "我是文本内容！");
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
                    v.startDragAndDrop(data, builder, v, 0);
                } else {
                    v.startDrag(data, builder, v, 0);
                }
                return true;
            }
        });
        frame.setOnDragListener(new View.OnDragListener() {
            @Override
            public boolean onDrag(View v, DragEvent event) {
                //获取事件
                int action = event.getAction();
                switch (action) {
                    case DragEvent.ACTION_DRAG_STARTED:
                        btn.setVisibility(View.INVISIBLE);
                        Log.d("csz", "开始拖拽");
                        break;
                    case DragEvent.ACTION_DRAG_ENDED:
                        Log.d("csz", "结束拖拽");
                        break;
                    case DragEvent.ACTION_DRAG_ENTERED:
                        Log.d("csz", "拖拽的view进入监听的view时");
                        break;
                    case DragEvent.ACTION_DRAG_EXITED:
                        Log.d("csz", "拖拽的view离开监听的view时");
                        frame.setBackgroundColor(Color.BLUE);
                        break;
                    case DragEvent.ACTION_DRAG_LOCATION:
                        float x = event.getX();
                        float y = event.getY();
                        frame.setBackgroundColor(Color.RED);
                        Log.i("csz", "拖拽的view在监听view中的位置:x =" + x + ",y=" + y);
                        break;
                    case DragEvent.ACTION_DROP:
                        Log.i("csz", "释放拖拽的view");
                        if( event.getLocalState() != null){
                            View localState = (View) event.getLocalState();
                            FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                            ((ViewGroup) localState.getParent()).removeView(localState);
                            frame.addView(localState, layoutParams);
                            btn.setVisibility(View.VISIBLE);
                        }
                        break;
                }
                return true;
            }
        });
    }

4.OnApplyWindowInsetsListener处理WindowInsets

  root.setSystemUiVisibility(root.getSystemUiVisibility() | View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);
        final int paddingTop = root.getPaddingTop();
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT_WATCH) {
            root.setOnApplyWindowInsetsListener(new View.OnApplyWindowInsetsListener() {
                @Override
                public WindowInsets onApplyWindowInsets(View v, WindowInsets insets) {
                    root.setPadding(root.getPaddingLeft(), paddingTop + insets.getSystemWindowInsetTop(), root.getPaddingRight(), root.getPaddingBottom());
                    return insets;
                }
            });
            //这不是绝对必要的，但确实可以解决WindowInsets的分派方式
            if (root.isAttachedToWindow()) {
                root.requestApplyInsets();
            } else {
                root.addOnAttachStateChangeListener(new View.OnAttachStateChangeListener() {
                    @Override
                    public void onViewAttachedToWindow(View v) {
                        v.removeOnAttachStateChangeListener(this);
                        v.requestApplyInsets();
                    }
                    @Override
                    public void onViewDetachedFromWindow(View v) {
                    }
                });
            }
        }

5.getGlobalVisibleRect(rect,null) 获取在根视图上的位置

6.getHitRect(rect) 获取在父视图上的位置（left,top,right,bottom)

7.设置触控和声音反馈

btn.setHapticFeedbackEnabled(true);
btn.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS,HapticFeedbackConstants.FLAG_IGNORE_GLOBAL_SETTING);
btn.playSoundEffect(SoundEffectConstants.CLICK);

8.setActivated(true) 激活视图，例如Toolbar激活后会有阴影效果

9.setDuplicateParentStateEnabled)(false) 设置父类的状态不会传递给自身，如selected，checked等

10.setClipBounds对视图裁剪，不会影响原有宽高

 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
      btn.setClipBounds(new Rect(0,0,btn.getWidth()/2,btn.getHeight()/2));
 }

11.StateListAnimator为view的state状态改变加动画

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
      StateListAnimator stateListAnimator = new StateListAnimator();
      ObjectAnimator animator = ObjectAnimator.ofFloat(iv, "alpha", 0.5f, 1.f).setDuration(500);
      ObjectAnimator reverseAnimator = animator.clone();
      reverseAnimator.setFloatValues(1.f, 0.5f);
      stateListAnimator.addState(new int[]{android.R.attr.state_selected}, animator);
      stateListAnimator.addState(new int[]{-android.R.attr.state_selected}, reverseAnimator);
      iv.setStateListAnimator(stateListAnimator);
      iv.setSelected(lefted = !lefted);
}

12.ColorStateList为view的state状态改变颜色，或者TextView的字体颜色

  ColorStateList stateList = new ColorStateList(new int[][]{{android.R.attr.state_selected, android.R.attr.state_checked}, {-android.R.attr.state_selected, -android.R.attr.state_checked}}, new int[]{Color.BLUE, Color.RED});
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            ColorStateListDrawable drawable = new ColorStateListDrawable(stateList);
            iv.setBackground(drawable);
        }

下面对ViewGroup的拓展使用进行说明：

1.ViewGroup.OnHierarchyChangeListener 监听视图的添加和移除

2.updateViewLayout 更新child的LayoutParams