Android实现View的任意拖动

安卓实现View的拖曳有几种方法，都不外乎改变View的坐标，并且重绘，于是，只要能够改变之就可以。

可以自定义View，重写OnTouchEvent(MotionEvent event)，可以在Activity 的onTouch()方法中监听手指在屏幕上的位置变化实现，也可以设置View的OnTouch监听。

自定义View的方式：

import android.content.Context;import android.os.Build;import android.support.annotation.Nullable;import android.support.annotation.RequiresApi;import android.util.AttributeSet;import android.view.MotionEvent;import android.widget.ImageView;/** *自定义的view，能够随意拖动。 * */public class DragView extends ImageView {    public DragView(Context context) {        super(context);    }    public DragView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);    }    public DragView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)    public DragView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {        super(context, attrs, defStyleAttr, defStyleRes);    }    private float downX;    private float downY;    private long downTime;    @Override    public boolean onTouchEvent(MotionEvent event) {        super.onTouchEvent(event);        if (this.isEnabled()) {            switch (event.getAction()) {                case MotionEvent.ACTION_DOWN:                    downX = event.getX();                    downY = event.getY();                    break;                case MotionEvent.ACTION_MOVE:                    final float xDistance = event.getX() - downX;                    final float yDistance = event.getY() - downY;                    if (xDistance != 0 && yDistance != 0) {                        int l = (int) (getLeft() + xDistance);                        int r = (int) (getRight() + xDistance);                        int t = (int) (getTop() + yDistance);                        int b = (int) (getBottom() + yDistance);                        this.layout(l, t, r, b);                    }                    break;                case MotionEvent.ACTION_UP:                    setPressed(false);                    break;                case MotionEvent.ACTION_CANCEL:                    setPressed(false);                    break;            }            return true;        }        return false;    }}

通过设置onTouch监听的方式，封装成工具类，方便重用：

import android.view.MotionEvent;import android.view.View;import android.view.ViewGroup;/** * 这个工具可以使任何一个view进行拖动。 *  */public class DragViewUtil {    public static void drag(View v){        drag(v,0);    }    /**     * 拖动View方法     * @param v view     * @param delay 延迟     */    public static void drag(View v,long delay){        v.setOnTouchListener(new TouchListener(delay));    }    private static class  TouchListener  implements View.OnTouchListener {        private float downX;        private float downY;        private long downTime;        private long delay;        private TouchListener() {        }        private TouchListener(long delay) {            this.delay = delay;        }        @Override        public boolean onTouch(View v, MotionEvent event) {            switch (event.getAction()) {                case MotionEvent.ACTION_DOWN:                    downX = event.getX();                    downY = event.getY();                    downTime = System.currentTimeMillis();                    break;                case MotionEvent.ACTION_MOVE:                    if(System.currentTimeMillis() - downTime>= delay){                    final float xDistance = event.getX() - downX;                    final float yDistance = event.getY() - downY;                    if (xDistance != 0 && yDistance != 0) {                        int l = (int) (v.getLeft() + xDistance);                        int r = (int) (v.getRight() + xDistance);                        int t = (int) (v.getTop() + yDistance);                        int b = (int) (v.getBottom() + yDistance);                        v.layout(l, t, r, b);                        ViewGroup.LayoutParams p = v.getLayoutParams();                    }                    }                    break;            }            return false;        }        }}

调用方法：

View view = findViewById(R.id.xxx);

DragViewUtil.drag(view);

运行预览：

Android实现View的任意拖动_第1张图片

项目地址：https://github.com/Mingyueyixi/DragView

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