Android 可自由拖动的View

概述

近期写过一个可自由拖动的View。
需求是能在屏幕中随意拖动这个View，然后如果View最终停止在屏幕左边就想左边靠边，如果停止在屏幕右边就向右边靠边。

本文是直接把该控件设置成了一个View。
也可以使用PopupWindow来做。
本人使用到的场景需要根据父布局来隐藏和显示，所以就不适合使用PopupWindow了。

注意：这个View适合隐藏了ActionBar的情况，如果没有隐藏ActionBar的话还需要开发者根据自己的情况适配一下。

demo

源码

MainActivity

	public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        MoveView moveView=findViewById(R.id.mv_main);
        moveView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this,"test click",Toast.LENGTH_SHORT).show();
            }
        });
    }

}

activity_main

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">


    <com.example.testprojectandroid.ui.MoveView
        android:id="@+id/mv_main"
        android:layout_width="100dp"
        android:layout_height="100dp"/>
</LinearLayout>

MoveView

public class MoveView extends RelativeLayout {

    //X和y代表 view中心点的位置
    private float currX;
    private float currY;
    private float lastX;
    private float lastY;

    private float width;
    private float height;

    //记录每次的最终位置
    private int left;
    private int right;
    private int top;
    private int bottom;

    //data
    private boolean hasMovingLong = false; //判断时候移动很大，如果移动过，即使回到原位，也不会触发点击事件

    private View.OnClickListener clickListener;


    public MoveView(Context context) {
        super(context);
    }

    public MoveView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MoveView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        init();
    }

    private void init() {
        //此处设置内容，测试就直接设置为黑色背景
        this.setBackgroundColor(Color.BLACK);

    }


    /**
     * 保证第一次点击的时候currX和currY已经有值
     */
    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);
        currX = (l + r) / 2;
        currY = (t + b) / 2;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        super.onTouchEvent(event);
        if (this.isEnabled()) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_MOVE:
                    currX = event.getRawX();
                    currY = event.getRawY();

                    if (Math.abs(lastX - currX) > width || Math.abs(lastY - currY) > height) {
                        hasMovingLong = true;
                    }

                    left = (int) (currX - width / 2);
                    top = (int) (currY - height / 2);
                    right = (int) (currX + width / 2);
                    bottom = (int) (currY + height / 2);

                    this.layout(left, top, right, bottom);
                    break;
                case MotionEvent.ACTION_DOWN:
                    width = getWidth();
                    height = getHeight();
                    lastX = currX;
                    lastY = currY;
                    break;
                case MotionEvent.ACTION_UP:
                    currX = event.getRawX();
                    currY = event.getRawY();

                    //如果移动距离很小，认为是点击
                    if (!hasMovingLong) {
                        if (Math.abs(lastX - currX) < width / 2 && Math.abs(lastY - currY) < height / 2) {
                            if (clickListener != null) {
                                clickListener.onClick(MoveView.this);
                            }
                        }
                    } else {
                        hasMovingLong = false;
                    }

                    updateViewLocation();

                    break;
            }
        }
        return true;
    }

    //更新view的位置
    private void updateViewLocation() {
        float parentWidth = ((View) getParent()).getWidth();

        //如果在屏幕左边
        if (parentWidth / 2 > currX) {
            currX = width / 2;
        } else {
            currX = parentWidth - width / 2;
        }

        left = (int) (currX - width / 2);
        top = (int) (currY - height / 2);
        right = (int) (currX + width / 2);
        bottom = (int) (currY + height / 2);

        this.layout(left, top, right, bottom);
    }

    @Override
    public void setOnClickListener(@Nullable View.OnClickListener l) {
        clickListener = l;
    }

}