android View使用及源码分析_android view源码分析

代码路径
frameworks/base/core/java/android/widget/
frameworks/base/core/java/android/view/
常见组件继承关系如下

1.View.java

实现的接口如下

1. Drawable.Callback 绘图相关，有三个方法

implements Drawable.Callback  //绘图相关
    有三个接口，实现如下
 @Override
    public void invalidateDrawable(@NonNull Drawable drawable) {
        if (verifyDrawable(drawable)) {
            final Rect dirty = drawable.getDirtyBounds(); //获取一个矩形
            final int scrollX = mScrollX;
            final int scrollY = mScrollY;
 
            invalidate(dirty.left + scrollX, dirty.top + scrollY,
                    dirty.right + scrollX, dirty.bottom + scrollY);
            rebuildOutline();
        }
    }
//Schedules an action on a drawable to occur at a specified time
 public void scheduleDrawable(@NonNull Drawable who, @NonNull Runnable what, long when);
//Schedules an action on a drawable to occur at a specified time
public void unscheduleDrawable(@NonNull Drawable who, @NonNull Runnable what);
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2.KeyEvent.Callback 按键相关，有四个方法

boolean onKeyDown(int keyCode, KeyEvent event); //按钮按下
boolean onKeyLongPress(int keyCode, KeyEvent event); //长按
boolean onKeyUp(int keyCode, KeyEvent event);  //按钮松开
boolean onKeyMultiple(int keyCode, int count, KeyEvent event);//按键重复
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2.TextView

官方文档https://developer.android.google.cn/reference/android/widget/TextView

1.addTextChangedListener(输入文本监听）

TextWatcher中有三个方法，beforeTextChanged，onTextChanged和afterTextChanged

public void addTextChangedListener(TextWatcher watcher) {  //文本监听
       if (mListeners == null) {
           mListeners = new ArrayList<TextWatcher>();
       }
       mListeners.add(watcher); //添加到mListeners中
   }
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2.为啥输入文本会监听到相关的动作

 TextView 中的setText方法中定义了一个 mChangeWatcher来监听文本的变化，为子类ChangeWatcher的对象
1

子类ChangeWatcher 中有beforeTextChanged，onTextChanged，afterTextChanged， onSpanChanged，onSpanAdded， onSpanRemoved等方法
以onTextChanged为例，源码如下

private class ChangeWatcher implements TextWatcher, SpanWatcher {
        public void onTextChanged(CharSequence buffer, int start, int before, int after) {
            if (DEBUG_EXTRACT) {
                Log.v(LOG_TAG, "onTextChanged start=" + start
                        + " before=" + before + " after=" + after + ": " + buffer);
            }
            TextView.this.handleTextChanged(buffer, start, before, after);
 
            if (AccessibilityManager.getInstance(mContext).isEnabled()
                    && (isFocused() || isSelected() && isShown())) {
                sendAccessibilityEventTypeViewTextChanged(mBeforeText, start, before, after);
                mBeforeText = null;
            }
        }
 
}
//handleTextChanged
 void handleTextChanged(CharSequence buffer, int start, int before, int after) {
       。。。
        resetErrorChangedFlag();
        sendOnTextChanged(buffer, start, before, after);
        onTextChanged(buffer, start, before, after);
    }
//sendOnTextChanged
 void sendOnTextChanged(CharSequence text, int start, int before, int after) {
        if (mListeners != null) {
            final ArrayList<TextWatcher> list = mListeners;
            final int count = list.size();
            for (int i = 0; i < count; i++) {
                list.get(i).onTextChanged(text, start, before, after);//调用添加的listener中的onTextChanged
            }
        }
 
        if (mEditor != null) mEditor.sendOnTextChanged(start, before, after);
    }
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3.Button

官方文档https://developer.android.google.cn/reference/android/widget/Button

1.setOnClickListener，定义在View.java中

public void setOnClickListener(@Nullable OnClickListener l) {
        if (!isClickable()) {
            setClickable(true);
        }
        getListenerInfo().mOnClickListener = l;  //子类ListenerInfo
    }
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点击按钮的堆栈打印如下

查看View中的performClick，源码如下

public boolean performClick() {
       。。。
       final boolean result;
       final ListenerInfo li = mListenerInfo;
       if (li != null && li.mOnClickListener != null) {
           playSoundEffect(SoundEffectConstants.CLICK);
           li.mOnClickListener.onClick(this); //调用onClick
           result = true;
       } else {
           result = false;
       }
       return result;
   }
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3.EditText 继承TextView

官方文档https://developer.android.google.cn/reference/android/widget/EditText
1.setOnFocusChangeListener，定义在View.java中

public void setOnFocusChangeListener(OnFocusChangeListener l) {
        getListenerInfo().mOnFocusChangeListener = l;
    }
protected void onFocusChanged(boolean gainFocus, @FocusDirection int direction,
            @Nullable Rect previouslyFocusedRect) {   //焦点改变时会调用这里
     li.mOnFocusChangeListener.onFocusChange(this, gainFocus);
}
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堆栈打印如下

4.View.java中定义的事件

static class ListenerInfo {
        protected OnFocusChangeListener mOnFocusChangeListener; //对应setOnFocusChangeListener
        private ArrayList<OnLayoutChangeListener> mOnLayoutChangeListeners; //对应addOnLayoutChangeListener
        protected OnScrollChangeListener mOnScrollChangeListener;  //对应setOnScrollChangeListener
        private CopyOnWriteArrayList<OnAttachStateChangeListener> mOnAttachStateChangeListeners; //addOnAttachStateChangeListener
        public OnClickListener mOnClickListener;   //setOnClickListener
        protected OnLongClickListener mOnLongClickListener;  //setOnLongClickListener
        protected OnContextClickListener mOnContextClickListener; //setOnContextClickListener
        protected OnCreateContextMenuListener mOnCreateContextMenuListener; //setOnCreateContextMenuListener
        private OnKeyListener mOnKeyListener;  //setOnKeyListener
        private OnTouchListener mOnTouchListener;  //setOnTouchListener
        private OnHoverListener mOnHoverListener;  //setOnHoverListener
        private OnGenericMotionListener mOnGenericMotionListener; //setOnGenericMotionListener
        private OnDragListener mOnDragListener; //setOnDragListener
        private OnSystemUiVisibilityChangeListener mOnSystemUiVisibilityChangeListener;//setOnSystemUiVisibilityChangeListener
        OnApplyWindowInsetsListener mOnApplyWindowInsetsListener;//setOnApplyWindowInsetsListener
        OnCapturedPointerListener mOnCapturedPointerListener; //setOnCapturedPointerListener
    }
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