本文详细介绍 Android 开发中 ListView 的使用技巧，包括基本配置、动态更新数据、实现弹性滚动及滑动隐藏 Toolbar 效果等。此外，还展示了如何通过手势识别实现左划删除功能。
生活本来就不容易啊，而我们的不努力只会让生活变得更加无赖。
相信大家在学习过程当中对ListView一定不会陌生，基本我们要用到列表时第一时间会想到它，虽然在Android5.0时Google推出了RecyclerView企图取代它，而且在这段期间内RecyclerView基本上已经可以满足取代ListView的能力（我始终觉得秒现瀑布流效果非常牛），但我觉得还是需要认真学习ListView，这两天结合《Android群英传》的学习，写一下ListView的学习笔记。 ###ListView的简单使用：
- activity_main.xml
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:divider="@android:color/transparent"
android:dividerHeight="1dp"
android:id="@+id/list_view"/>```
* 代码使用:
* 适配器MyAdapter
复制代码public class MyAdapter extends BaseAdapter{
private List<String> list;
private LayoutInflater inflater;
public MyAdapter(Context context ,List<String> list) {
this.list = list;
inflater = LayoutInflater.from(context);
}
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int i) {
return null;
}
@Override
public long getItemId(int i) {
return i;
}
@Override
public View getView(int i, View view, ViewGroup viewGroup) {
viewHolder viewHolder = null;
if (view == null){
viewHolder = new viewHolder();
view = inflater.inflate(R.layout.view_holder,null);
viewHolder.textView = (TextView) view.findViewById(R.id.text_view);
view.setTag(viewHolder);
}else{
viewHolder = (MyAdapter.viewHolder) view.getTag();
}
viewHolder.textView.setText(list.get(i));
return view;
}
class viewHolder{
TextView textView;
}
复制代码}```
- MainActivity.java
public class MainActivity extends AppCompatActivity implements View.OnTouchListener {
private List<String> list ;
private MyAdapter adapter;
private ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}
private void initView() {
listView = (ListView) findViewById(R.id.list_view);
list = initList();
adapter = new MyAdapter(this,list);
listView.setAdapter(adapter);
//设置ListView为空时的显示图片
listView.setEmptyView(findViewById(R.id.emptyImage));
//滑动监听事件
listView.setOnTouchListener(this);
//设置点击事件
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
}
});
}
private List<String> initList() {
List<String> mdatas = new ArrayList<>();
for (int i = 'A';i<'z';++i){
mdatas.add(""+(char)i);
}
return mdatas;
}
@Override
public boolean onTouch(View view, MotionEvent motionEvent) {
switch (motionEvent.getAction()){
case MotionEvent.ACTION_DOWN:
//触摸时调用 Toast.makeText(this,"Down",Toast.LENGTH_SHORT).show();
break;
case MotionEvent.ACTION_MOVE:
//滑动时调用
Toast.makeText(this,"Move",Toast.LENGTH_SHORT).show();
break;
case MotionEvent.ACTION_UP:
//离开时调用
Toast.makeText(this,"Up",Toast.LENGTH_SHORT).show();
break;
}
return false;
}
}```
* 效果
------
### 常用属性:
- 设置ListView为空时的显示布局
复制代码//设置ListView为空时的显示图片 listView.setEmptyView(findViewById(R.id.emptyImage));```
- 动态增加数据及设置ListView位置
/**
* 动态增加
*/
public void btnAdd(){
list.addAll(Arrays.asList("Hello","Hi","WelCome"));
adapter.notifyDataSetChanged();
listView.setSelection(0);
}```
- 具有弹性的ListView
复制代码/** *修改overScrollBy方法中的maxOverScrollY值 / private int mMaxOverSrcollY = 5; //适配分辨率 private void getmMaxOverSrcollY(){ DisplayMetrics metrics = context.getResources().getDisplayMetrics(); float density = metrics.density; mMaxOverSrcollY = (int) (densitymMaxOverSrcollY); }
@Override
protected boolean overScrollBy(int deltaX, int deltaY,
int scrollX, int scrollY,
int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY,
boolean isTouchEvent) {
return super.overScrollBy(deltaX, deltaY, scrollX,
scrollY, scrollRangeX, scrollRangeY, maxOverScrollX,
mMaxOverSrcollY, isTouchEvent);
}```
复制代码-
为ListView设置滑动时Toolbar的隐藏 其实逻辑很简单,就是为ListView设置headView,然后借助OnTouchListener获取滑动点的坐标改变大小,实现滑上滑下距离的判断.最后借助简单的动画实现隐藏和出现.
-
代码
//获取系统认为的最低滑动距离
private float mTouchSlop;
//定义两个变量进行两次滑动距离的判断
private float mFirstY , mCurrentY;
//声明flag标志Toolbar状态
private int direction;
//声明boolean判断状态
private boolean mShow;
private Toolbar mToorbar;
private Animator mAnimator;
mToorbar = (Toolbar) findViewById(R.id.tool_bar);
setSupportActionBar(mToorbar);
//添加headView
View head = new View(this);
head.setLayoutParams(new AbsListView.LayoutParams(AbsListView.LayoutParams.MATCH_PARENT,
(int) getResources().getDimension(R.dimen.abc_action_bar_default_height_material)));
listView.addHeaderView(head);
//获取最低滑动距离
mTouchSlop = ViewConfiguration.get(this).getScaledTouchSlop();
@Override
public boolean onTouch(View view, MotionEvent motionEvent) {
switch (motionEvent.getAction()){
case MotionEvent.ACTION_DOWN:
//触摸时调用,获取第一次位置
mFirstY = motionEvent.getY();
break;
case MotionEvent.ACTION_MOVE:
//滑动时调用
mCurrentY = motionEvent.getY();
if (mCurrentY - mFirstY > mTouchSlop){
direction = 0;//向下滑
}else if (mFirstY - mCurrentY >mTouchSlop){
direction = 1;//向上滑
}
if (direction == 1){
if (mShow){
toolbarAnim(0);//隐藏
mShow = !mShow;
}
}else if (direction == 0){
if (!mShow){
toolbarAnim(1);
mShow = !mShow;
}
}
break;
case MotionEvent.ACTION_UP:
//离开时调用
break;
}
return false;
}
//控制head布局状态
private void toolbarAnim(int flag) {
if (mAnimator != null && mAnimator.isRunning()){
mAnimator.cancel();
}
if (flag == 0){
mAnimator = ObjectAnimator.ofFloat(mToorbar,"translationY",
mToorbar.getTranslationY(),0);
}else {
mAnimator = ObjectAnimator.ofFloat(mToorbar,"translationY",
mToorbar.getTranslationY(),mToorbar.getHeight());
}
mAnimator.start();
}```
* 效果
### 常见拓展
在学习ListView的,顺便学习了一下Hyman的一篇技术博客,是关于仿QQ实现左划删除的效果的,其实代码的逻辑也很简单,就是利用事件分发机制实现手势的判断,利用dispatchTouchEvent以及onTouchEvent这两个方法对手势进行判断,最后利用Button对所在Item进行delete
* 整体预览
* xml文件
* enter_ainm.xml
复制代码- activity_main.xml
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.lqg.deletedemo.MainActivity">
<com.lqg.deletedemo.MyListView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/delete_listview">
</com.lqg.deletedemo.MyListView>
</RelativeLayout>```
* style.xml
复制代码- MyListView.java
public class MyListView extends ListView {
/**
* 用户滑动的最小距离
*/
private int mTouchSlop;
/**
* 是否响应滑动
*/
private boolean isSliding;
/**
* 手指按下时的x坐标
*/
private int FirstX;
/**
* 手指按下时的y坐标
*/
private int FirstY;
/**
* 手指移动时的x坐标
*/
private int NextX;
/**
* 手指移动时的y坐标
*/
private int NextY;
private LayoutInflater mInflater;
private PopupWindow mPopupWindow;
private int mPopupWindowHeight;
private int mPopupWindowWidth;
private Button mDelBtn;
/**
* 为删除按钮提供一个回调接口
*/
private DelButtonClickListener mListener;
/**
* 当前手指触摸的View
*/
private View mCurrentView;
/**
* 当前手指触摸的位置
*/
private int mCurrentViewPos;
/**
* 必要的一些初始化
*
*/
public MyListView(Context context, AttributeSet attrs) {
super(context, attrs);
mInflater = LayoutInflater.from(context);
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
View view = mInflater.inflate(R.layout.del_btn, null);
mDelBtn = (Button) view.findViewById(R.id.btn_del);
mPopupWindow = new PopupWindow(view, LinearLayout.LayoutParams.WRAP_CONTENT,
LinearLayout.LayoutParams.WRAP_CONTENT);
/**
* 先调用下measure,否则拿不到宽和高
*/
mPopupWindow.getContentView().measure(0, 0);
mPopupWindowHeight = mPopupWindow.getContentView().getMeasuredHeight();
mPopupWindowWidth = mPopupWindow.getContentView().getMeasuredWidth();
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
int x = (int) ev.getX();
int y = (int) ev.getY();
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
FirstX = x;
FirstY = y;
/**
* 如果当前popupWindow显示，则直接隐藏，然后屏蔽ListView的touch事件的下传
*/
if (mPopupWindow.isShowing()) {
dismissPopWindow();
return false;
}
// 获得当前手指按下时的item的位置
mCurrentViewPos = pointToPosition(FirstX, FirstY);
// 获得当前手指按下时的item
View view = getChildAt(mCurrentViewPos - getFirstVisiblePosition());
mCurrentView = view;
break;
case MotionEvent.ACTION_MOVE:
NextX = x;
NextY = y;
int dx = NextX - FirstX;
int dy = NextY - FirstY;
/**
* 判断是否是从右到左的滑动
*/
if (NextX < FirstX && Math.abs(dx) > mTouchSlop && Math.abs(dy) < mTouchSlop) {
isSliding = true;
}
break;
}
return super.dispatchTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
int action = ev.getAction();
/**
* 如果是从右到左的滑动才相应
*/
if (isSliding) {
switch (action) {
case MotionEvent.ACTION_MOVE:
int[] location = new int[2];
// 获得当前item的位置x与y
mCurrentView.getLocationOnScreen(location);
// 设置popupWindow的动画
mPopupWindow.setAnimationStyle(R.style.btn_del_Animotion);
mPopupWindow.update();
mPopupWindow.showAtLocation(mCurrentView, Gravity.START | Gravity.TOP,
location[0] + mCurrentView.getWidth(), location[1] + mCurrentView.getHeight() / 2
- mPopupWindowHeight / 2);
// 设置删除按钮的回调
mDelBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if (mListener != null) {
mListener.clickHappend(mCurrentViewPos);
mPopupWindow.dismiss();
}
}
});
break;
case MotionEvent.ACTION_UP:
isSliding = false;
}
// 相应滑动期间屏幕itemClick事件，避免发生冲突
return true;
}
return super.onTouchEvent(ev);
}
/**
* 隐藏popupWindow
*/
private void dismissPopWindow() {
if (mPopupWindow != null && mPopupWindow.isShowing()) {
mPopupWindow.dismiss();
}
}
public void setDelButtonClickListener(DelButtonClickListener listener) {
this.mListener = listener;
}
public interface DelButtonClickListener {
public void clickHappend(int position);
}
}```
* MainActivity.java
复制代码public class MainActivity extends AppCompatActivity {
private MyListView listView;
private ArrayAdapter<String> adapter;
private List<String> list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView =(MyListView) findViewById(R.id.delete_listview);
list = new ArrayList<>();
for (int i = 1;i<100;++i){
list.add(""+i);
}
adapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,list);
listView.setAdapter(adapter);
listView.setDelButtonClickListener(new MyListView.DelButtonClickListener() {
@Override
public void clickHappend(int position) {
adapter.remove(adapter.getItem(position));
adapter.notifyDataSetChanged();
}
});
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) { Toast.makeText(MainActivity.this,position+"onClick",Toast.LENGTH_SHORT).show();
}
});
}
复制代码}```
- 代码如上,其实这相当大部分是模仿hyman的代码,不过出于学习的目的.所以写在自己的笔记.HongYang博客传送门 http://blog.youkuaiyun.com/lmj623565791/
- 效果
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