ringtone分析（一）

DefaultRingtonePreference单击后出现的是一个AlertDialog，但是在DefaultRingtonePreference没看见任何构造Dialog的信息，显然构建在父类RingtonePreference中，
在RingtonePreference.java中：

	protected void onClick() { //注意这对DefaultRingtonePreference单机事件左的处理有跳转
			// Launch the ringtone picker
			Intent intent = new Intent(RingtoneManager.ACTION_RINGTONE_PICKER);
			onPrepareRingtonePickerIntent(intent);
			getPreferenceManager().getActivity().startActivityForResult(intent, mRequestCode);
	}

这里的startActivityForResult就跳转到了RingtonePickerActivity.java文件里面，
在RingtonePickerActivity.java中：

        public void onClick(DialogInterface dialog, int which) {
        Log.i(TAG,"------onClick----");
        boolean positiveResult = which == DialogInterface.BUTTON_POSITIVE;
        
        // Stop playing the previous ringtone
        mRingtoneManager.stopPreviousRingtone();
        
        if (positiveResult) {
            Intent resultIntent = new Intent();
            Uri uri = null;
            
            if (mClickedPos == mDefaultRingtonePos) {
                // Set it to the default Uri that they originally gave us
                uri = mUriForDefaultItem;
            } else if (mClickedPos == mSilentPos) {
                // A null Uri is for the 'Silent' item
                uri = null;
            } else {
                uri = mRingtoneManager.getRingtoneUri(getRingtoneManagerPosition(mClickedPos));
            }

            resultIntent.putExtra(RingtoneManager.EXTRA_RINGTONE_PICKED_URI, uri);
            setResult(RESULT_OK, resultIntent);
        } else {
            setResult(RESULT_CANCELED);
        }

会把当前选中的那个铃声的URI返回给在RingtonePreference.java，