这个控件是仿制高德地图下面的可拖拽列表栏做的。实现主要就是一个LinearLayout响应用户手势拖拽，有全屏，半屏，和隐藏三个模式。依据拖拽到松手的位置的y坐标占屏幕的百分比来确定对应的模式位置，再利用动画移动到对应的模式位置。
完整的代码我会贴在文末。
DragUpDownLinearlayout.gif
一、确定三个模式的位置
我这里使用的是铺满contentView，占contentView的1/3,和全部在隐藏在下面只留一个拖拽条三个模式。contentView的概念我这里大概讲一下，android的布局是在decorView这个根布局下的，分为titleView和ContentView。
titleView放的是ActionBar等位置，如果设置noActionBar就没有titleView的位置了。
而contentView就是我们平时Activity里面onCreate中setContent的那个ContentView，相当于我们的内容布局的父布局，在这个控件我们计算主要依靠它来完成。
三个模式的height也就是Y坐标值是：
switch (customMode) {
case TOP_MODE:
top = topHeight;
bottom = getHeight() + topHeight;
break;
case MIDDLE_MODE:
top = middleHeight;
bottom = getHeight() + middleHeight;
break;
case BOTTOM_MODE:
int topUp = contentViewHeight - indicatorHeightPx;
top = topUp;
bottom = getHeight() + topUp;
break;
}
主要看一个top的赋值 这个top就是我们要设给onLayout的参数，控件的顶部的y坐标。
topHeight contentView里面除了这个控件之外 顶部还有其他控件占位置，我们需要加上这个控件的高度，不然会覆盖掉它，例如上面有一个自定义的标题栏没有加入到Toolbar的位置而是放在contentView里面，那么这个情况就需要被考虑。这个值我是由外部初始化的时候计算传入的。
middleHeight 计算方法：
contentViewHeight = ((Activity) getContext()).getWindow().
findViewById(Window.ID_ANDROID_CONTENT).getMeasuredHeight();
middleHeight = (contentViewHeight / 3) * 2;
上面说的是1/3但这里写的是2/3是因为android屏幕的Y坐标是向下的，我们需要在1/3的位置就需要让控件向下移动2/3。
**topUp ** 相当于留一个indicatorHeightPx（那个灰色的长条）的位置 其他全部在屏幕下方。
OK，位置的计算就只有这些了。
二、拖拽控件
接下来就是主要的功能拖拽了。
这里需要用到手势类GestureDetector，不熟悉的同学可以去搜索一下看一看，它里面封装了各种手势的触发条件和触发回调，使用起来比自己重写onTouch再分类要有效率的多。它的使用就是在onTouch方法里将参数传递给它：
public boolean onTouch(View view, MotionEvent event) {
mGestureDetector.onTouchEvent(event);
return true;
}
它的实现类：
@Override
public boolean onScroll(MotionEvent motionEvent, MotionEvent motionEvent1, float distanceX, float distanceY) {
int y = (int) motionEvent1.getY();
// 获取本次移动的距离
int dy = y - y0;
int top = getTop();
int bottom = getBottom();
if (top <= topHeight && dy < 0) {
// 高出顶部 则不改变位置防止超出顶部
return false;
}
layout(getLeft(), (top + dy),
getRight(), (bottom + dy));
isScrolling = true;
return false;
}
@Override
public boolean onFling(MotionEvent motionEvent, MotionEvent motionEvent1, float x, float speedY) {
float v = motionEvent1.getRawY() - rawYDown;
switch (customMode) {
case TOP_MODE:
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + (middleHeight - getY()));
customMode = MIDDLE_MODE;
break;
case MIDDLE_MODE:
if (v > 0) {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + contentViewHeight - getY() - indicatorHeightPx);
customMode = BOTTOM_MODE;
} else {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() - getY() + topHeight);
customMode = TOP_MODE;
}
break;
case BOTTOM_MODE:
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + (middleHeight - getY()));
customMode = MIDDLE_MODE;
break;
default:
}
animator.setDuration(500);
animator.start();
// 动画结束时，将控件的translation偏移量转化为Top值，便于计算
animator.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
float translationY = getTranslationY();
setTranslationY(0);
layout(getLeft(), (int) (getTop() + translationY),
getRight(), (int) (getBottom() + translationY));
animator = null;
}
});
isScrolling = false;
hasFiling = true;
return true;
}
就使用了这两个方法。思路就是在onScroll里面响应拖拽调用layout方法不断修改布局位置，然后结束的时候通常情况下回触发onFiling方法，在这个方法里计算位置开始动画等将控件移动到指定的位置。
还需要注意的是当你慢慢拖拽的时候会触发不了onFiling这个方法 所以我在这里添加了一个hasFiling的标志位去判断onFiling是否调用了，没调用的话在onTouch里面再处理一下：
@Override
public boolean onTouch(View view, MotionEvent event) {
mGestureDetector.onTouchEvent(event);
// 是否有执行filing
if (event.getAction() == MotionEvent.ACTION_UP) {
if (!hasFiling) {
isScrolling = false;
// 松手时固定位置 计算占屏幕的百分比
float yUP = getTop();
float i = yUP / screenHeight;
if (i < 0.30) {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() - getY() + topHeight);
customMode = TOP_MODE;
} else if (i < 0.75) {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + (middleHeight - getY()));
customMode = MIDDLE_MODE;
} else {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + contentViewHeight - getY() - indicatorHeightPx);
customMode = BOTTOM_MODE;
}
animator.setDuration(500);
animator.start();
// 动画结束时，将控件的translation偏移量转化为Top值，便于计算
animator.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
float translationY = getTranslationY();
setTranslationY(0);
layout(getLeft(), (int) (getTop() + translationY),
getRight(), (int) (getBottom() + translationY));
animator = null;
}
});
}
}
return true;
}
整体的逻辑还是看文末的代码吧 这里只是介绍一下功能的实现。
三、解决事件分发冲突
一般在这里内部都会有一个ListView控件来展示数据，它与我们的这个控件就会有滑动冲突。
解决方法是用外部拦截法来解决。
我在这里新建了一个接口来回调给调用类
public void setInterceptCallBack(RequestInterceptCallBack interceptCallBack) {
this.interceptCallBack = interceptCallBack;
}
public interface RequestInterceptCallBack {
boolean canIntercept(boolean isDown);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
boolean intercept = false;
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
y0 = (int) ev.getY();
rawYDown = ev.getRawY();
intercept = false;
hasFiling = false;
break;
case MotionEvent.ACTION_MOVE:
float dy = ev.getY() - y0;
Log.i(TAG, "dy" + dy);
if (Math.abs(dy) < 7 || animator != null || (customMode == TOP_MODE && dy < 0)) {
// 移动过小视为点击事件。不拦截 或者 动画尚未结束 本次不拦截
intercept = false;
} else if (dy > 0) {
intercept = interceptCallBack.canIntercept(true);
} else {
intercept = interceptCallBack.canIntercept(false);
}
break;
case MotionEvent.ACTION_UP:
intercept = false;
break;
}
return intercept;
}
canIntercept(boolean isDown)这个参数我设置的是手势是否下滑，如果是recyclerView则在方法重写里面判断
recyclerView.canScrollVertically(-1);这个方法。
例如：
@Override
public boolean canIntercept(boolean isDown) {
if (isDown) {
Log.i(TAG, "-1: " + recyclerView.canScrollVertically(-1));
return !recyclerView.canScrollVertically(-1);
} else {
Log.i(TAG, "1: " + recyclerView.canScrollVertically(1));
return !recyclerView.canScrollVertically(1);
}
}
其中的逻辑需要自己揣摩一下。
四、最后调用类的初始化工作
在Activity中：
dragUpDownLinearLayout.setInterceptCallBack(this);
dragUpDownLinearLayout.setTopHeight(relativeLayout.getMeasuredHeight());
handler.post(new Runnable() {
@Override
public void run() {
dragUpDownLinearLayout.setLocation(DragUpDownLinearLayout.MIDDLE_MODE);
dragUpDownLinearLayout.setVisibility(View.VISIBLE);
}
});
我这里是直接设置的Middle_Mode模式。布局里设置的空间隐藏，设置完再显示，不这样的话会出现闪一下的变化位置，比较不好，其实也可以进入的时候走一个动画。这些都看爱好和需求吧。
代码
/**
* Created by Vito
*/
public class DragUpDownLinearLayout extends LinearLayout implements View.OnTouchListener,
GestureDetector.OnGestureListener {
public final static String TAG = "DragUpDownLinearLayout";
public final static int TOP_MODE = 1;
public final static int MIDDLE_MODE = 2;
public final static int BOTTOM_MODE = 3;
public int customMode = 0;
// 手势监听对象
private GestureDetector mGestureDetector;
// 拖拽条的高度
private final static int indicatorHeight = 30;
private int indicatorHeightPx;
// 中间位置的高度
private int middleHeight;
// contentView（去掉状态栏、toolbar和导航栏部分）的高度
private int contentViewHeight;
// 顶部其他控件的高度
private int topHeight;
// 屏幕的高度
private float screenHeight;
// 滑动开始手指落点
private int y0;
private float rawYDown;
// 第一次加载标志位
private boolean isFirstLayout = true;
// 是否拦截事件接口回调，用于判断子控件的是否可滑动
private RequestInterceptCallBack interceptCallBack;
// 动画对象
private ObjectAnimator animator = null;
private static final String ANIMATOR_MODE = "translationY";
// 是否触发了Filing方法，未触发交由onTouch方法完成移动
private boolean hasFiling;
// 是否在滚动触发的layout的标志位
private boolean isScrolling;
public DragUpDownLinearLayout(Context context) {
this(context, null);
}
public DragUpDownLinearLayout(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public DragUpDownLinearLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context);
}
@SuppressLint("ClickableViewAccessibility")
private void init(Context context) {
// 界面
indicatorHeightPx = dp2px(indicatorHeight);
setBackgroundColor(Color.WHITE);
FrameLayout frameLayout = new FrameLayout(context);
frameLayout.setLayoutParams(
new LinearLayoutCompat.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, indicatorHeightPx));
addView(frameLayout);
View view = new View(context);
FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(dp2px(75), dp2px(8));
params.gravity = Gravity.CENTER;
view.setLayoutParams(params);
view.setBackgroundResource(R.drawable.shape_drag_up_down_indicator);
frameLayout.addView(view);
// 获取屏幕的高
DisplayMetrics dm = context.getResources().getDisplayMetrics();
screenHeight = dm.heightPixels;
setOnTouchListener(this);
mGestureDetector = new GestureDetector(getContext(), this);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
boolean intercept = false;
if (interceptCallBack != null) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
y0 = (int) ev.getY();
rawYDown = ev.getRawY();
intercept = false;
hasFiling = false;
break;
case MotionEvent.ACTION_MOVE:
float dy = ev.getY() - y0;
Log.i(TAG, "dy" + dy);
if (Math.abs(dy) < 7 || animator != null || (customMode == TOP_MODE && dy < 0)) {
// 移动过小视为点击事件。不拦截 或者 动画尚未结束 本次不拦截
intercept = false;
} else if (dy > 0) {
intercept = interceptCallBack.canIntercept(true);
} else {
intercept = interceptCallBack.canIntercept(false);
}
break;
case MotionEvent.ACTION_UP:
intercept = false;
break;
}
}
return intercept;
}
@Override
public boolean onTouch(View view, MotionEvent event) {
mGestureDetector.onTouchEvent(event);
// 是否有执行filing
if (event.getAction() == MotionEvent.ACTION_UP) {
if (!hasFiling) {
isScrolling = false;
// 松手时固定位置 计算占屏幕的百分比
float yUP = getTop();
float i = yUP / screenHeight;
if (i < 0.30) {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() - getY() + topHeight);
customMode = TOP_MODE;
} else if (i < 0.75) {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + (middleHeight - getY()));
customMode = MIDDLE_MODE;
} else {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + contentViewHeight - getY() - indicatorHeightPx);
customMode = BOTTOM_MODE;
}
animator.setDuration(500);
animator.start();
// 动画结束时，将控件的translation偏移量转化为Top值，便于计算
animator.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
float translationY = getTranslationY();
setTranslationY(0);
layout(getLeft(), (int) (getTop() + translationY),
getRight(), (int) (getBottom() + translationY));
animator = null;
}
});
}
}
return true;
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
Log.e(TAG, "onLayout" + t);
if (isFirstLayout) {
contentViewHeight = ((Activity) getContext()).getWindow().
findViewById(Window.ID_ANDROID_CONTENT).getMeasuredHeight();
middleHeight = (contentViewHeight / 3) * 2;
isFirstLayout = false;
Log.e(TAG, "contentViewHeight" + contentViewHeight);
} else {
Log.e(TAG, "isScrolling" + isScrolling);
if (!isScrolling) {
switch (customMode) {
case TOP_MODE:
t = topHeight;
b = getHeight() + topHeight;
break;
case MIDDLE_MODE:
t = middleHeight;
b = getHeight() + middleHeight;
break;
case BOTTOM_MODE:
int topUp = contentViewHeight - indicatorHeightPx;
t = topUp;
b = getHeight() + topUp;
break;
}
setTop(t);
setBottom(b);
}
}
super.onLayout(changed, l, t, r, b);
}
/**
* 设置位置，同于指定初始化位置
*/
public void setLocation(int mode) {
switch (mode) {
case TOP_MODE:
layout(getLeft(),
topHeight,
getRight(),
getHeight() + topHeight);
customMode = TOP_MODE;
break;
case MIDDLE_MODE:
layout(getLeft(), middleHeight,
getRight(), middleHeight + getHeight());
customMode = MIDDLE_MODE;
break;
case BOTTOM_MODE:
int topUp = contentViewHeight - indicatorHeightPx;
layout(getLeft(), topUp,
getRight(), topUp + getHeight());
customMode = BOTTOM_MODE;
break;
}
}
@Override
public boolean onDown(MotionEvent motionEvent) {
return false;
}
@Override
public boolean onScroll(MotionEvent motionEvent, MotionEvent motionEvent1, float distanceX, float distanceY) {
int y = (int) motionEvent1.getY();
// 获取本次移动的距离
int dy = y - y0;
int top = getTop();
int bottom = getBottom();
if (top <= topHeight && dy < 0) {
// 高出顶部 则不改变位置防止超出顶部
return false;
}
layout(getLeft(), (top + dy),
getRight(), (bottom + dy));
isScrolling = true;
return false;
}
@Override
public boolean onFling(MotionEvent motionEvent, MotionEvent motionEvent1, float x, float speedY) {
float v = motionEvent1.getRawY() - rawYDown;
switch (customMode) {
case TOP_MODE:
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + (middleHeight - getY()));
customMode = MIDDLE_MODE;
break;
case MIDDLE_MODE:
if (v > 0) {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + contentViewHeight - getY() - indicatorHeightPx);
customMode = BOTTOM_MODE;
} else {
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() - getY() + topHeight);
customMode = TOP_MODE;
}
break;
case BOTTOM_MODE:
animator = ObjectAnimator.ofFloat(DragUpDownLinearLayout.this, ANIMATOR_MODE,
getTranslationY(), getTranslationY() + (middleHeight - getY()));
customMode = MIDDLE_MODE;
break;
default:
}
animator.setDuration(500);
animator.start();
// 动画结束时，将控件的translation偏移量转化为Top值，便于计算
animator.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
float translationY = getTranslationY();
setTranslationY(0);
layout(getLeft(), (int) (getTop() + translationY),
getRight(), (int) (getBottom() + translationY));
animator = null;
}
});
isScrolling = false;
hasFiling = true;
return true;
}
@Override
public void onLongPress(MotionEvent motionEvent) {
}
@Override
public void onShowPress(MotionEvent motionEvent) {
}
@Override
public boolean onSingleTapUp(MotionEvent motionEvent) {
return false;
}
private int dp2px(float dipValue) {
final float scale = getContext().getResources().getDisplayMetrics().density;
return (int) (dipValue * scale + 0.5f);
}
public void setInterceptCallBack(RequestInterceptCallBack interceptCallBack) {
this.interceptCallBack = interceptCallBack;
}
public interface RequestInterceptCallBack {
boolean canIntercept(boolean isDown);
}
/**
* 重新请求一次contentView 因为toolbar将它往下顶了一部分，也就是加一个偏移量
*/
public void resetContentViewHeight(int off) {
contentViewHeight = ((Activity) getContext()).getWindow().
findViewById(Window.ID_ANDROID_CONTENT).getMeasuredHeight() - off;
middleHeight = (contentViewHeight / 3) * 2;
Log.e(TAG, "resetContentViewHeight" + contentViewHeight);
}
/**
* 设置顶部高度
*/
public void setTopHeight(int topHeight) {
this.topHeight = topHeight;
}
}