如何在Android中使用可移动元素正确更新布局？

debugcn 发表于 Dev

拉斐尔·斯库比斯（Rafael Skubisz）

今天，我试图创建一个具有4个ImageViews和一个ListView的布局，并根据ImageView的位置更新listview的位置。

一个SS向您展示我正在尝试做的事情：

在此处输入图片说明

如您所见，一旦我们拉动“灰色手柄”，ListView位置就会更新。一切正常，但是在移动手柄时图形不平滑但结结巴巴。

我用于此的代码如下所示；

btn.setOnTouchListener(new OnTouchListener() {
        @Override
        public boolean onTouch(View view, MotionEvent me) {
            if (me.getAction() == MotionEvent.ACTION_DOWN) {
                status = START_DRAGGING;
            }
            if (me.getAction() == MotionEvent.ACTION_UP) {
                status = STOP_DRAGGING;
                Log.i("Drag", "Stopped Dragging");
            } else if (me.getAction() == MotionEvent.ACTION_MOVE) {
                if (status == START_DRAGGING) {
                    System.out.println("Dragging");

                    GestureImageView image1 = (GestureImageView) findViewById(R.id.image1);
                    GestureImageView image2 = (GestureImageView) findViewById(R.id.image2);

                    ImageView header = (ImageView) findViewById(R.id.imageHeader);

                    RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
                            RelativeLayout.LayoutParams.WRAP_CONTENT,
                            RelativeLayout.LayoutParams.WRAP_CONTENT);

                    lp.addRule(RelativeLayout.CENTER_HORIZONTAL);
                    margin1 = (int) me.getRawY() - 100;
                    if (margin1 < header.getHeight() - btn.getHeight() / 3)
                        margin1 = header.getHeight() - btn.getHeight() / 3;
                    else if (margin1 > layout.getHeight() - 1.5
                            * btn.getHeight() - btn3.getHeight())
                        margin1 = (int) (layout.getHeight() - 1.5
                                * btn.getHeight() - btn3.getHeight());
                    lp.topMargin = margin1;
                    btn.setLayoutParams(lp);

                    if (margin1 >= margin2 - 35) {
                        RelativeLayout.LayoutParams newlp = new RelativeLayout.LayoutParams(
                                RelativeLayout.LayoutParams.WRAP_CONTENT,
                                RelativeLayout.LayoutParams.WRAP_CONTENT);

                        newlp.addRule(RelativeLayout.CENTER_HORIZONTAL);
                        margin2 = margin1 + 35;
                        newlp.topMargin = margin2;
                        btn2.setLayoutParams(newlp);

                        RelativeLayout.LayoutParams newlp2 = new RelativeLayout.LayoutParams(
                                RelativeLayout.LayoutParams.WRAP_CONTENT,
                                RelativeLayout.LayoutParams.FILL_PARENT);
                        newlp2.addRule(RelativeLayout.ABOVE, btn2.getId());
                        newlp2.addRule(RelativeLayout.BELOW, header.getId());
                        newlp2.bottomMargin = -(15 + margin2);
                        image2.setLayoutParams(newlp2);
                        image2.setAdditionalY(image2.getHeight(),
                                margin2 - 85, image2.getScaledHeight()
                                        - margin2 - 85);
                    }

                    RelativeLayout.LayoutParams lp3 = new RelativeLayout.LayoutParams(
                            RelativeLayout.LayoutParams.WRAP_CONTENT,
                            RelativeLayout.LayoutParams.FILL_PARENT);
                    lp3.addRule(RelativeLayout.ABOVE, btn.getId());
                    lp3.addRule(RelativeLayout.BELOW, header.getId());
                    lp3.bottomMargin = -(15 + margin1);
                    image1.setLayoutParams(lp3);
                    image1.setAdditionalY(image1.getHeight(), margin1 - 50,
                            image1.getScaledHeight() - margin1 - 50);
                }
            }
            return false;
        }
    });

如您所见，我向“灰色手柄”添加了一个侦听器，并在移动时更新了“布局”规则并计算了边距。有一个更好的方法吗？

提前致谢，以帮助我。

EDIT: I forgot to add that the bigger the listView the bigger the stutter and I think it's caused by the listView rebuilding all views while changing its position.

EDIT2: I did some testing, added logs and while moving the listview, all views get rebuilt everytime the listview moves. Is there a way to stop this? Maybe make it rebuild once the user stops moving the images?

Rafael Skubisz

Solved the problem by optimizing "getView" in my ListView.

For everyone that has problems with listViews:

If convertView exists dont create a new view
Use ViewHolders
Never create a Typeface in getView, create all typefaces on calling the constructor
If you fill the List with data from a database create a class where you will be keeping all needed data, instead of calling the DB every new view is created.

本文收集自互联网，转载请注明来源。

如有侵权，请联系[email protected] 删除。