涉及的知識(shí)點(diǎn)：ListView的復(fù)用，倒計(jì)時(shí)，啟動(dòng)線程刷新UI
由于項(xiàng)目有個(gè)需求，就是點(diǎn)擊ListView的某個(gè)item的button，開始倒計(jì)時(shí)。所以花了些時(shí)間寫了個(gè)Demo,先上效果圖
看起來(lái)是不是感覺(jué)很簡(jiǎn)單，但一開始走了很多坑。首先是ListView的復(fù)用問(wèn)題。點(diǎn)擊一個(gè)item的button開始倒計(jì)時(shí)，但是把ListView滑下來(lái),下面的item會(huì)復(fù)用前面的item,導(dǎo)致它沒(méi)有點(diǎn)擊也會(huì)倒計(jì)時(shí)。產(chǎn)生這個(gè)原因是因?yàn)槲以诋?dāng)我點(diǎn)擊button時(shí)，對(duì)TextView設(shè)置
Text，也就是倒計(jì)時(shí)，而那些沒(méi)有點(diǎn)擊的item沒(méi)有被setText，所以會(huì)導(dǎo)致復(fù)用，時(shí)間錯(cuò)亂。ListView的數(shù)據(jù)源是動(dòng)態(tài)的話，由于復(fù)用往往會(huì)使顯示的數(shù)據(jù)錯(cuò)亂。
切入正題,說(shuō)說(shuō)實(shí)現(xiàn)的思路。
我們使用一個(gè)boolean變量標(biāo)記button的點(diǎn)擊事件，一旦點(diǎn)擊了，我們就開啟倒計(jì)時(shí)，并標(biāo)記為true。然后開啟一個(gè)線程，把ListvView所有的TextView傳到這個(gè)線程中，通過(guò)一個(gè)死循環(huán)，每隔一秒刷新一次UI,將每個(gè)TextView進(jìn)行setText,如果數(shù)據(jù)類的成員變量isPressed為true,就設(shè)置為倒計(jì)時(shí)的時(shí)間，如果不是，就設(shè)為“00：00”，思路就這樣。
首先我們需要一個(gè)數(shù)據(jù)類
public class Bean {
private String text;//button的text
private int time;//TextView顯示的時(shí)間
private boolean isPressed;//標(biāo)記button是否按下。
private TimerEnitity timerEnitity;//進(jìn)行倒計(jì)時(shí)的類
public TimerEnitity getTimerEnitity() {
return timerEnitity;
}
public void setTimerEnitity(TimerEnitity timerEnitity) {
this.timerEnitity = timerEnitity;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
public int getTime() {
return time;
}
public boolean isPressed() {
return isPressed;
}
public void setPressed(boolean isPressed) {
this.isPressed = isPressed;
}
public void setTime(int time) {
this.time = time;
}
}
我們還需要一個(gè)倒計(jì)時(shí)的類，通過(guò)這個(gè)類我們可以實(shí)時(shí)獲取倒計(jì)時(shí)的時(shí)間。我們使用android的倒計(jì)時(shí)類CountDownTimer，繼承它作為內(nèi)部類，一旦初始化TimerEnitity，我們就開始倒計(jì)時(shí)，并實(shí)時(shí)獲取倒計(jì)時(shí)的時(shí)間。
public class TimerEnitity {
private int timeLength;
private MyTimer timer;
private Bean bean;
public TimerEnitity(int timeLength,Bean bean) {
this.timeLength = timeLength;
this.bean=bean;
timer = new MyTimer(timeLength,999);
timer.start();
}
public int getsurplusTime(){
return this.bean.getTime();
}
public void setTimeLength(int timeLength) {
this.timeLength = timeLength;
}
public class MyTimer extends CountDownTimer{
public MyTimer(long millisInFuture, long countDownInterval) {
super(millisInFuture, countDownInterval);
}
@Override
public void onTick(long l) {
Log.e("time",l+"");
bean.setTime((int) l);//通過(guò)系統(tǒng)不斷地回調(diào)這個(gè)方法，time值不斷地被改變，我們就可以獲取倒計(jì)時(shí)的時(shí)間。
}
@Override
public void onFinish() {
bean.setTime(0);
}
}
}
接下來(lái)就是對(duì)Activity和Adapter的操作了，先上代碼。
public class MainActivity extends AppCompatActivity {
private ListView listView;
private TimeAdapter adapter;
private TimeThread timeThread;
private List<Bean> data = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.listview);
initData();
timeThread = new TimeThread();
timeThread.start();
adapter = new TimeAdapter(listView);
listView.setAdapter(adapter);
}
private void initData() {
for (int i = 0; i < 30; i++) {
Bean bean = new Bean();
bean.setText("item" + i);
bean.setTime(0);
bean.setPressed(false);
data.add(bean);
}
}
class TimeAdapter extends BaseAdapter {
private ListView listView;
public TimeAdapter(ListView listView){
this.listView = listView;
}
private LayoutInflater inflater = LayoutInflater.from(MainActivity.this);
@Override
public int getCount() {
return data.size();
}
@Override
public Object getItem(int i) {
return (Bean)data.get(i);
}
@Override
public long getItemId(int i) {
return i;
}
@Override
public View getView(final int i, View view, ViewGroup viewGroup) {
ViewHolder holder = null;
final Bean bean = (Bean) getItem(i);
if (view == null) {
view = inflater.inflate(R.layout.item, null);
holder = new ViewHolder();
holder.textView = (TextView) view.findViewById(R.id.text);
holder.button = (Button) view.findViewById(R.id.btn);
view.setTag(holder);
} else {
holder = (ViewHolder) view.getTag();
}
timeThread.setTextViewToList(holder.textView,bean);
holder.button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
bean.setPressed(true);
TimerEnitity enitity = new TimerEnitity(60000,bean);
bean.setTimerEnitity(enitity);
timeThread.setChangedBean(i,bean);
}
});
holder.textView.setText(MyUtils.timeToString(bean.getTime()));
holder.button.setText(data.get(i).getText());
return view;
}
public class ViewHolder {
public TextView textView;
public Button button;
}
}
}
上面的代碼關(guān)鍵在兩個(gè)地方
第1個(gè)地方
timeThread = new TimeThread();
timeThread.start();
上面我們講過(guò)，這個(gè)線程一直不斷地更新UI，所以應(yīng)該在onCreate方法里啟動(dòng)
第2個(gè)地方
timeThread.setTextViewToList(holder.textView,bean);
holder.button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
TimerEnitity enitity = new TimerEnitity(60000,bean);
bean.setPressed(true);
bean.setTimerEnitity(enitity);
timeThread.setChangedBean(i,bean);
}
});
holder.textView.setText(MyUtils.timeToString(bean.getTime()));
holder.button.setText(data.get(i).getText());
線程的操作涉及到bean數(shù)據(jù)類，所以要將Textview和Bean傳過(guò)去.然后在button的點(diǎn)擊事件里，我們標(biāo)記為true，并啟動(dòng)倒計(jì)時(shí)。這里需要留意一下，即使我們?cè)趏nClick方法里將bean的變量值進(jìn)行修改，比如bean.setPressed(true);bean.setTimerEnitity(enitity);但是點(diǎn)擊事件是不定時(shí)的，所以此時(shí)的修改并不影響到已經(jīng)傳遞到線程里的bean數(shù)據(jù)，所以需要寫個(gè)方法將修改后的變量傳過(guò)去timeThread.setChangedBean(i,bean);
我們來(lái)看一下TimeThread的代碼，在run方法中，我們通過(guò)一個(gè)死循環(huán)，每隔一秒發(fā)送一個(gè)消息，在handler中對(duì)所有的TextView遍歷，點(diǎn)擊過(guò)的，就將TextView設(shè)置倒計(jì)時(shí)的時(shí)間，沒(méi)有點(diǎn)擊的就設(shè)置為默認(rèn)時(shí)間。
public class TimeThread extends Thread {
private List<TextView> textViews;
private List<Bean> beans = new ArrayList<>();
private boolean isRun=true;
private Handler mHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
int cache = -1;
for(int i=0;i<textViews.size();i++){
if (beans.get(i).isPressed()) {
textViews.get(i).setText(MyUtils.timeToString(beans.get(i).getTimerEnitity().getsurplusTime()));
}else textViews.get(i).setText("00:00");
}
}
};
public TimeThread(){
textViews = new ArrayList<TextView>();
}
@Override
public void run() {
while (isRun){
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
mHandler.sendEmptyMessage(0);
}
}
public void setTextViewToList(TextView textView,Bean bean){
textViews.add(textView);
beans.add(bean);
}
public void setChangedBean(int postion,Bean bean){
beans.get(postion).setPressed(bean.isPressed());
beans.get(postion).setTimerEnitity(bean.getTimerEnitity());
}
}
最后還需要將時(shí)間轉(zhuǎn)化一下格式。
public class MyUtils {
public static String timeToString(int timeLength) {
int min = Math.round((timeLength/1000)/ 60);
int second = Math.round((timeLength/1000) % 60);
Log.e("min",min+"");
Log.e("second",second+"");
if (timeLength <=0) {
return "00:00";
} else if (timeLength >0) {
if (min < 10 && second < 10)
return "0" + min +":"+ "0" + second;
if (min < 10 && second >= 10)
return "0" + min +":"+ second;
if (min >= 10 && second < 10)
return min +":"+ "0" + second;
if (min >= 10 && second >= 10)
return min +":" + second;
}
return null;
}
}
想查看demo請(qǐng)從github下載https://github.com/MRKCH/itemcounter
