2018-10-15

引用

/**

• Constructs a new spinner with the given context, the supplied attribute
• set, default styles, popup mode (one of {@link #MODE_DIALOG} or
• {@link #MODE_DROPDOWN}), and the theme against which the popup should be
• inflated.
• @param context The context against which the view is inflated, which

•            provides access to the current theme, resources, etc.
  

• @param attrs The attributes of the XML tag that is inflating the view.
• @param defStyleAttr An attribute in the current theme that contains a

•                 reference to a style resource that supplies default
  

•                 values for the view. Can be 0 to not look for
  

•                 defaults.
  

• @param defStyleRes A resource identifier of a style resource that

•                supplies default values for the view, used only if
  

•                defStyleAttr is 0 or can not be found in the theme.
  

•                Can be 0 to not look for defaults. * @param mode Constant describing how the user will select choices from
  

•         the spinner.
  

• @param popupTheme The theme against which the dialog or dropdown popup

•               should be inflated. May be {@code null} to use the
  

•               view theme. If set, this will override any value
  

•               specified by
  

•               {@link android.R.styleable#Spinner_popupTheme}.
  

• @see #MODE_DIALOG // SpinnerMode="dialog"
• @see #MODE_DROPDOWN // SpinnerMode="dropDown"
  */
  public Spinner(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes, int mode,
  Theme popupTheme) {
  super(context, attrs, defStyleAttr, defStyleRes);
  final TypedArray a = context.obtainStyledAttributes(
  attrs, R.styleable.Spinner, defStyleAttr, defStyleRes);
  if (popupTheme != null) {
  mPopupContext = new ContextThemeWrapper(context, popupTheme);
  } else {
  final int popupThemeResId = a.getResourceId(R.styleable.Spinner_popupTheme, 0);
  if (popupThemeResId != 0) {
  mPopupContext = new ContextThemeWrapper(context, popupThemeResId);
  } else {
  mPopupContext = context;
  }
  }
  if (mode == MODE_THEME) {
  mode = a.getInt(R.styleable.Spinner_spinnerMode, MODE_DIALOG);
  }
  switch (mode) {
  case MODE_DIALOG: {// 当SpinnerMode为dialog时
  mPopup = new DialogPopup();
  mPopup.setPromptText(a.getString(R.styleable.Spinner_prompt));
  break;
  }
  case MODE_DROPDOWN: {// 当SpinnerMode为dropDown时
  // 在这里新建了一个DropdownPopup用来展示下拉列表的内容，关于DropdownPopup源码请看下一片段
  final DropdownPopup popup = new DropdownPopup(
  mPopupContext, attrs, defStyleAttr, defStyleRes);
  final TypedArray pa = mPopupContext.obtainStyledAttributes(
  attrs, R.styleable.Spinner, defStyleAttr, defStyleRes);
  mDropDownWidth = pa.getLayoutDimension(R.styleable.Spinner_dropDownWidth,
  ViewGroup.LayoutParams.WRAP_CONTENT);
  if (pa.hasValueOrEmpty(R.styleable.Spinner_dropDownSelector)) {
  popup.setListSelector(pa.getDrawable(
  R.styleable.Spinner_dropDownSelector));
  }
  popup.setBackgroundDrawable(pa.getDrawable(R.styleable.Spinner_popupBackground));
  popup.setPromptText(a.getString(R.styleable.Spinner_prompt));
  pa.recycle();
  mPopup = popup;
  mForwardingListener = new ForwardingListener(this) {
  @Override
  public ShowableListMenu getPopup() {
  return popup;
  }
  @Override
  public boolean onForwardingStarted() {
  if (!mPopup.isShowing()) {
  mPopup.show(getTextDirection(), getTextAlignment());
  }
  return true;
  }
  };
  break;
  }
  }
  mGravity = a.getInt(R.styleable.Spinner_gravity, Gravity.CENTER);
  mDisableChildrenWhenDisabled = a.getBoolean(
  R.styleable.Spinner_disableChildrenWhenDisabled, false);
  a.recycle();
  // Base constructor can call setAdapter before we initialize mPopup.
  // Finish setting things up if this happened.
  if (mTempAdapter != null) {
  setAdapter(mTempAdapter);
  mTempAdapter = null;
  }
  }