ANDROID控件拖拽

import android.annotation.SuppressLint;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ViewGroup;
import android.widget.FrameLayout;

import com.longmen.teacher.R;
import com.longmen.teacher.common.SimpleCallback;
import com.longmen.teacher.utils.DPUtils;

public class DragView extends FrameLayout {

    private int mLastX;
    private int mLastY;
    private int mParentWidth;
    private int mParentHeight;

    private DragTextView.TextBean mTextBean;

    private SimpleCallback mCallback;

    public DragView(@NonNull Context context) {
        super(context);
    }

    public DragView(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public DragView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @SuppressLint("ClickableViewAccessibility")
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        ViewGroup mViewGroup = (ViewGroup) getParent();
        if (null != mViewGroup && mParentWidth == 0) {
            mParentWidth = mViewGroup.getWidth() - (int) getResources().getDimension(R.dimen.note_width);
            mParentHeight = mViewGroup.getHeight();
        }
        int ea = event.getAction();
        switch (ea) {
            case MotionEvent.ACTION_DOWN:
                mLastX = (int) event.getRawX();//获取触摸事件触摸位置的原始X坐标
                mLastY = (int) event.getRawY();
            case MotionEvent.ACTION_MOVE:
                //event.getRawX();获得移动的位置
                int dx = (int) event.getRawX() - mLastX;
                int dy = (int) event.getRawY() - mLastY;
                updateLayout(dx, dy);
                mLastX = (int) event.getRawX();
                mLastY = (int) event.getRawY();
                postInvalidate();
                break;
            case MotionEvent.ACTION_UP:
                if (mCallback != null) {
                    DragTextView.TextBean textBean = mTextBean;
                    textBean.x = getLeft();
                    textBean.y = getBottom();
                    textBean.t = getTop();
                    textBean.r = getRight();
                    mCallback.onResult(textBean);
                    setVisibility(GONE);
                }
                mTextBean = null;
                break;
        }
        return true;
    }

    private void updateLayout(int dx, int dy) {
        int l = getLeft() + dx;
        int b = getBottom() + dy;
        int r = getRight() + dx;
        int t = getTop() + dy;

        //下面判断移动是否超出屏幕
        if (l < 0) {
            l = 0;
            r = l + getWidth();
        }
        if (t < 0) {
            t = 0;
            b = t + getHeight();
        }
        if (r > mParentWidth) {
            r = mParentWidth;
            l = r - getWidth();
        }
        if (b > mParentHeight) {
            b = mParentHeight;
            t = b - getHeight();
        }
        layout(l, t, r, b);
    }

    public void addDragView(String text, float size, SimpleCallback callback) {
        removeAllViews();
        setVisibility(VISIBLE);
        postInvalidate();
        mCallback = callback;
        DragTextView mTextView = new DragTextView(getContext());
        mTextBean = mTextView.getTextBean(text.trim(), size);
        addView(mTextView, new FrameLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));

        FrameLayout.LayoutParams lp = new FrameLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
        int w = DPUtils.getScreenWidth(getContext()) - (int) getResources().getDimension(R.dimen.note_width);
        int vW = (int) mTextView.getPaint().measureText(text);
        if (vW > w) {
            lp.rightMargin = (int) getResources().getDimension(R.dimen.note_width);
        }
        lp.topMargin = 200;
        lp.leftMargin = 200;
        setLayoutParams(lp);
    }
}