Android实现随意拖动View效果-技术圈

项目过程中需要实现View能在页面中随意的拖动，刚开始实现是用悬浮球的形式进行实现，因为之前项目中用过，实现后发现用户每次安装后，都有权限的限制，甚至有些用户关闭悬浮球权限之后，不知道怎么在手机上打开悬浮球的权限，这样的话用户体验很不好，所以自己重新自定义实现在页面中拖动，不需要请求权限。

1、先来看看效果图：

2、自定义随意拖动View：

package com.dragdemo;
import android.annotation.SuppressLint;import android.content.Context;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.widget.ImageView;
/** * 随意拖动的view */@SuppressLint("AppCompatCustomView")public class DragView extends ImageView {    private int width;    private int height;    private int screenWidth;    private int screenHeight;    private Context context;    //是否拖动    private boolean isDrag = false;
    public boolean isDrag() {        return isDrag;    }
    public DragView(Context context, AttributeSet attrs) {        super(context, attrs);        this.context = context;    }
    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        width = getMeasuredWidth();        height = getMeasuredHeight();        screenWidth = ScreenUtil.getScreenWidth(context);        screenHeight = ScreenUtil.getScreenHeight(context) - getStatusBarHeight();    }
    public int getStatusBarHeight() {        int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android");        return getResources().getDimensionPixelSize(resourceId);    }
    private float downX;    private float downY;
    @Override    public boolean onTouchEvent(MotionEvent event) {        super.onTouchEvent(event);        if (this.isEnabled()) {            switch (event.getAction()) {                case MotionEvent.ACTION_DOWN:                    isDrag = false;                    downX = event.getX();                    downY = event.getY();                    break;                case MotionEvent.ACTION_MOVE:                    Log.e("kid", "ACTION_MOVE");                    final float xDistance = event.getX() - downX;                    final float yDistance = event.getY() - downY;                    int l, r, t, b;                    //当水平或者垂直滑动距离大于10,才算拖动事件                    if (Math.abs(xDistance) > 10 || Math.abs(yDistance) > 10) {                        Log.e("kid", "Drag");                        isDrag = true;                        l = (int) (getLeft() + xDistance);                        r = l + width;                        t = (int) (getTop() + yDistance);                        b = t + height;                        //不划出边界判断,此处应按照项目实际情况,因为本项目需求移动的位置是手机全屏,                        // 所以才能这么写,如果是固定区域,要得到父控件的宽高位置后再做处理                        if (l < 0) {                            l = 0;                            r = l + width;                        } else if (r > screenWidth) {                            r = screenWidth;                            l = r - width;                        }                        if (t < 0) {                            t = 0;                            b = t + height;                        } else if (b > screenHeight) {                            b = screenHeight;                            t = b - height;                        }                        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;    }}

3、用到的工具类：

package com.dragdemo;
import android.content.Context;import android.util.DisplayMetrics;import android.view.Display;import android.view.View;import android.view.WindowManager;
public class ScreenUtil {    private static int width = 0;    private static int height = 0;    private static int showHeight = 0;    private static int statusHeight = 0;    private static float density = 0;
    public static int getScreenWidth(Context context) {        if (width == 0) {            WindowManager manager = (WindowManager) context                    .getSystemService(Context.WINDOW_SERVICE);            Display display = manager.getDefaultDisplay();            width = display.getWidth();        }        return width;    }
    public static int getScreenHeight(Context context) {        if (height == 0) {            WindowManager manager = (WindowManager) context                    .getSystemService(Context.WINDOW_SERVICE);            Display display = manager.getDefaultDisplay();            height = display.getHeight();        }        return height;    }
    public static int getScreenShowHeight(Context context) {        if (showHeight == 0) {            showHeight = getScreenHeight(context) - getStatusBarHeight(context);        }        return showHeight;    }
    public static int getStatusBarHeight(Context context) {        if (statusHeight > 0) {            return statusHeight;        }        Class<?> c = null;        Object obj = null;        java.lang.reflect.Field field = null;        int x = 0;        try {            c = Class.forName("com.android.internal.R$dimen");            obj = c.newInstance();            field = c.getField("status_bar_height");            x = Integer.parseInt(field.get(obj).toString());            statusHeight = context.getResources().getDimensionPixelSize(x);            return statusHeight;        } catch (Throwable e) {            e.printStackTrace();        }        return statusHeight;    }
    public static float getScreenDensity(Context context) {        if (density == 0) {            try {                DisplayMetrics dm = new DisplayMetrics();                WindowManager manager = (WindowManager) context                        .getSystemService(Context.WINDOW_SERVICE);                manager.getDefaultDisplay().getMetrics(dm);                density = dm.density;            } catch (Exception ex) {                ex.printStackTrace();                density = 1.0f;            }        }        return density;    }
    public static float getScreentMinLength(Context context) {        return getScreenHeight(context) > getScreenWidth(context) ? getScreenWidth(context)                : getScreenHeight(context);    }
    /**     * 根据指定k的系数获取屏幕在max范围内的最大长宽,默认宽比较小     *     * @param context     * @param k     * @return     */    public static DrawWrap getCutWrap(Context context, float k, float max) {        float tWidth = getScreenWidth(context);        float tHeight = getScreenHeight(context);        if (tWidth * max * k > tHeight) {            return new DrawWrap(tHeight * max / k, tHeight * max);        } else {            return new DrawWrap(tWidth * max, tWidth * max * k);        }    }
    public static class DrawWrap {        public float width;        public float height;
        public DrawWrap(float width, float height) {            this.width = width;            this.height = height;        }    }
    public static int dip2px(Context context, float dipValue) {        return (int) (dipValue * getScreenDensity(context) + 0.5f);    }
    /**     * 将sp值转换为px值，保证文字大小不变     *     * @param context     * @param spValue （DisplayMetrics类中属性scaledDensity）     * @return     */    public static int sp2px(Context context, float spValue) {        final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;        return (int) (spValue * fontScale + 0.5f);    }
    /**     * 根据手机的分辨率从 px(像素) 的单位 转成为 dp     */    public static int px2dip(Context context, float pxValue) {        final float scale = context.getResources().getDisplayMetrics().density;        return (int) (pxValue / scale + 0.5f);    }
    /**     * 获取屏幕中控件顶部位置的高度--即控件顶部的Y点     *     * @return     */    public static int getScreenViewTopHeight(View view) {        return view.getTop();    }
    /**     * 获取屏幕中控件底部位置的高度--即控件底部的Y点     *     * @return     */    public static int getScreenViewBottomHeight(View view) {        return view.getBottom();    }
    /**     * 获取屏幕中控件左侧的位置--即控件左侧的X点     *     * @return     */    public static int getScreenViewLeftHeight(View view) {        return view.getLeft();    }
    /**     * 获取屏幕中控件右侧的位置--即控件右侧的X点     *     * @return     */    public static int getScreenViewRightHeight(View view) {        return view.getRight();    }
    /*     * 获取控件宽     */    public static int getWidth(View view) {        int w = View.MeasureSpec.makeMeasureSpec(0,                View.MeasureSpec.UNSPECIFIED);        int h = View.MeasureSpec.makeMeasureSpec(0,                View.MeasureSpec.UNSPECIFIED);        view.measure(w, h);        return (view.getMeasuredWidth());    }
    /*     * 获取控件高     */    public static int getHeight(View view) {        int w = View.MeasureSpec.makeMeasureSpec(0,                View.MeasureSpec.UNSPECIFIED);        int h = View.MeasureSpec.makeMeasureSpec(0,                View.MeasureSpec.UNSPECIFIED);        view.measure(w, h);        return (view.getMeasuredHeight());    }}

4、XML文件：

    <com.dragdemo.DragView        android:id="@+id/iv_drag"        android:layout_width="80dp"        android:layout_height="80dp"        android:layout_gravity="center"        android:src="@drawable/function_night_open" />

5、MainActivity代码逻辑

package com.dragdemo;
import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Toast;
public class MainActivity extends AppCompatActivity {    DragView iv_drag;
    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        iv_drag = (DragView) findViewById(R.id.iv_drag);        iv_drag.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                if (!iv_drag.isDrag()) {                    Toast.makeText(MainActivity.this, "响应点击", Toast.LENGTH_SHORT).show();                }            }        });    }}

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