Android實現隨意拖動View效果

項目過程當中要實現能在頁面中隨意的拖動，剛開始實現是用懸浮球的形式進行實現，由於以前項目中用過，實現後發現用戶每次安裝後，都有權限的限制，甚至有些用戶關閉懸浮球權限以後，不知道怎麼在手機上打開懸浮球的權限，這樣的話用戶體驗很很差，因此本身從新自定義實如今頁面中拖動，不須要請求權限。

自定義隨意拖動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;

/**
 *隨意拖動的view
 */

@SuppressLint("AppCompatCustomView")
public class DragView extends ImageView {

    private int width;
    private int height;
    private int screenWidth;
    private int screenHeight;
    private Context context;

    //是否拖動
    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;
                    //當水平或者垂直滑動距離大於10,纔算拖動事件
                    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;
                        //不劃出邊界判斷,此處應按照項目實際狀況,由於本項目需求移動的位置是手機全屏,
                        // 因此才能這麼寫,若是是固定區域,要獲得父控件的寬高位置後再作處理
                        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;
    }

}

複製代碼

用到的工具類：

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);
	}

	/**
	 * 根據指定k的係數獲取屏幕在max範圍內的最大長寬,默認寬比較小
	 * 
	 * @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);
	}

	/**
	 * 將sp值轉換爲px值，保證文字大小不變
	 *
	 * @param context
	 * @param spValue
	 *            （DisplayMetrics類中屬性scaledDensity）
	 * @return
	 */
	public static int sp2px(Context context, float spValue) {
		final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
		return (int) (spValue * fontScale + 0.5f);
	}

	/**
	 * 根據手機的分辨率從 px(像素) 的單位 轉成爲 dp
	 */
	public static int px2dip(Context context, float pxValue) {
		final float scale = context.getResources().getDisplayMetrics().density;
		return (int) (pxValue / scale + 0.5f);
	}

	/**
	 * 獲取屏幕中控件頂部位置的高度--即控件頂部的Y點
	 * 
	 * @return
	 */
	public static int getScreenViewTopHeight(View view) {
		return view.getTop();
	}

	/**
	 * 獲取屏幕中控件底部位置的高度--即控件底部的Y點
	 * 
	 * @return
	 */
	public static int getScreenViewBottomHeight(View view) {
		return view.getBottom();
	}

	/**
	 * 獲取屏幕中控件左側的位置--即控件左側的X點
	 * 
	 * @return
	 */
	public static int getScreenViewLeftHeight(View view) {
		return view.getLeft();
	}

	/**
	 * 獲取屏幕中控件右側的位置--即控件右側的X點
	 * 
	 * @return
	 */
	public static int getScreenViewRightHeight(View view) {
		return view.getRight();
	}

	/*
	 * 獲取控件寬
	 */
	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());
	}

	/*
	 * 獲取控件高
	 */
	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());
	}

}

複製代碼

XML文件：

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

MainActivity:

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, "響應點擊", Toast.LENGTH_SHORT).show();
                }

            }
        });
    }
}

複製代碼

項目Demo連接：底部公衆號回覆 "隨意拖動View" 便可獲取。

如下是我的公衆號(longxuanzhigu)，以後發佈的文章會同步到該公衆號，方便交流學習Android知識及分享我的愛好文章：