Android之AlertController的源碼學習記錄

 這裏節選了AlertController的源碼，它是AlertDialog.Builder中非常重要的工具類，主要作用是根據Builder中配置好的參數來生成對應的Dialog。

我節選下面這段代碼的原因就是因爲我們通過AlertDialog.Builder創建的dialog，只要點擊Positive、Negative、Neutral等按鈕就會觸發dismiss方法，然後自行關閉。。。雖然大家都知道點擊按鈕之後會觸發dismiss，但是估計很少有人知道dismiss方法是通過什麼方式觸發的吧。。。所以我這波源碼追蹤，也算是溯源找真相了

另外安利一個查詢Android源碼的網站--->Android源碼

private final View.OnClickListener mButtonHandler = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            final Message m;
            if (v == mButtonPositive && mButtonPositiveMessage != null) {
                m = Message.obtain(mButtonPositiveMessage);
            } else if (v == mButtonNegative && mButtonNegativeMessage != null) {
                m = Message.obtain(mButtonNegativeMessage);
            } else if (v == mButtonNeutral && mButtonNeutralMessage != null) {
                m = Message.obtain(mButtonNeutralMessage);
            } else {
                m = null;
            }

            if (m != null) {
                m.sendToTarget();
            }

            // Post a message so we dismiss after the above handlers are executed
            mHandler.obtainMessage(ButtonHandler.MSG_DISMISS_DIALOG, mDialogInterface)
                    .sendToTarget();
        }
    };


private static final class ButtonHandler extends Handler {
        // Button clicks have Message.what as the BUTTON{1,2,3} constant
        private static final int MSG_DISMISS_DIALOG = 1;

        private WeakReference<DialogInterface> mDialog;

        public ButtonHandler(DialogInterface dialog) {
            mDialog = new WeakReference<DialogInterface>(dialog);
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {

                case DialogInterface.BUTTON_POSITIVE:
                case DialogInterface.BUTTON_NEGATIVE:
                case DialogInterface.BUTTON_NEUTRAL:
                    ((DialogInterface.OnClickListener) msg.obj).onClick(mDialog.get(), msg.what);
                    break;

                case MSG_DISMISS_DIALOG:
                    //這裏調用了dismiss方法
                    ((DialogInterface) msg.obj).dismiss();
            }
        }
    }