View在容器中有限的滑动

代码改造自任玉刚 《Android开发艺术探索》第三章《View的实践体系》
github地址是：
https://github.com/singwhatiwanna/android-art-res

原来的代码如下：

package com.ryg.chapter_3.ui;

import android.annotation.SuppressLint;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ViewConfiguration;
import android.widget.TextView;

import com.nineoldandroids.view.ViewHelper;

public class TestButton extends TextView {
    private static final String TAG = "TestButton";
    private int mScaledTouchSlop;
    // 分别记录上次滑动的坐标
    private int mLastX = 0;
    private int mLastY = 0;

    public TestButton(Context context) {
        this(context, null);
    }

    public TestButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public TestButton(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        mScaledTouchSlop = ViewConfiguration.get(getContext())
                .getScaledTouchSlop();
        Log.d(TAG, "sts:" + mScaledTouchSlop);
    }

    @SuppressLint("ClickableViewAccessibility")
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int x = (int) event.getRawX();
        int y = (int) event.getRawY();
        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN: {
            break;
        }
        case MotionEvent.ACTION_MOVE: {
            int deltaX = x - mLastX;
            int deltaY = y - mLastY;
            Log.d(TAG, "move, deltaX:" + deltaX + " deltaY:" + deltaY);
            int translationX = (int)ViewHelper.getTranslationX(this) + deltaX;
            int translationY = (int)ViewHelper.getTranslationY(this) + deltaY;
            ViewHelper.setTranslationX(this, translationX);
            ViewHelper.setTranslationY(this, translationY);
            break;
        }
        case MotionEvent.ACTION_UP: {
            break;
        }
        default:
            break;
        }

        mLastX = x;
        mLastY = y;
        return true;
    }
}

该组件可以做到自由在父容器中移动，甚至可以移动到父容器的外面，就是出现了直接消失的情况；
因此需要对其移动范围做一定的限制，限制在父容器中，上下左右4个边界均不超过父容器的边界，修改后如下：

package com.ryg.chapter_3.ui;

import android.annotation.SuppressLint;
import android.content.Context;
import android.support.v7.widget.AppCompatTextView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;


public class TestButton2 extends AppCompatTextView {
    private static final String TAG = "TestButton2";
    private int mScaledTouchSlop;
    // 分别记录上次滑动的坐标
    private int mLastX = 0;
    private int mLastY = 0;


    private int mParentWidth;
    private int mParentHeight;
    private int mWidth;
    private int mHeight;
    /**
     * 初始位置
     */
    private int mStartTop;
    private int mStartBottom;
    private int mStartLeft;
    private int mStartRight;

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        this.mHeight = getHeight();
        this.mWidth = getWidth();
    }

    public TestButton2(Context context) {
        this(context, null);
    }

    public TestButton2(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public TestButton2(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        //最小滑动距离：大于这个值时 触发移动
        mScaledTouchSlop = ViewConfiguration.get(getContext())
                .getScaledTouchSlop();
        Log.d(TAG, "sts:" + mScaledTouchSlop);
        post(new Runnable() {
            @Override
            public void run() {

                mParentWidth = ((View) getParent()).getWidth();
                mParentHeight = ((View) getParent()).getHeight();

                mWidth = getWidth();
                mHeight = getHeight();
                mStartTop = getTop();
                mStartBottom = getBottom();
                mStartLeft = getLeft();
                mStartRight = getRight();
                
            }
        });
    }

    @SuppressLint("ClickableViewAccessibility")
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int x = (int) event.getRawX();
        int y = (int) event.getRawY();
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN: {
                break;
            }
            case MotionEvent.ACTION_MOVE: {
                int deltaX = x - mLastX;
                int deltaY = y - mLastY;
                Log.d(TAG, "move, deltaX:" + deltaX + " deltaY:" + deltaY);
                int translationX = (int) this.getTranslationX() + deltaX;
                int translationY = (int) this.getTranslationY() + deltaY;
                //add by duoxioo start
                //ok
                if (translationX > mParentWidth - mStartRight) {
                    translationX = mParentWidth - mStartRight;
                } else if (translationX < -mStartLeft) {
                    translationX = -mStartLeft;
                }
                //ok


                //ok
                if (translationY > mParentHeight - mStartBottom) {
                    translationY = mParentHeight - mStartBottom;
                } else if (translationY < -mStartTop) {
                    translationY = -mStartTop;
                }
                //ok
                
                Log.d(TAG, "onTouchEvent: translationX = " + translationX);
                Log.d(TAG, "onTouchEvent: translationY = " + translationY);
                //add by duoxioo end

                this.setTranslationX(translationX);
                this.setTranslationY(translationY);
                break;
            }
            case MotionEvent.ACTION_UP: {
                break;
            }
            default:
                break;
        }

        mLastX = x;
        mLastY = y;
        return true;
    }
}

这样子可以有限的移动了，不会滑动到容器之外了。