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前言#xff1a;
之前讲解过livedata和viewmodel的简单使用#xff0c;也封装过room工具类#xff0c;本文是对livedata的简单封装和使用#xff0c;先是封装了一个简单的工具类#xff0c;然后实现了一个倒计时工具类的封装.
1.LiveD…Android中简单封装Livedata工具类
前言
之前讲解过livedata和viewmodel的简单使用也封装过room工具类本文是对livedata的简单封装和使用先是封装了一个简单的工具类然后实现了一个倒计时工具类的封装.
1.LiveDataHelper工具类
package com.example.livedatautilsdemo.helper;import androidx.annotation.NonNull;
import androidx.lifecycle.LifecycleOwner;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.Observer;import java.util.Map;
import java.util.WeakHashMap;/*** author: njb* date: 2023/7/31 0:10* desc:*/
public class LiveDataHelperTextends MutableLiveData {private final WeakHashMapObserverT, Boolean mObservers new WeakHashMap();Overridepublic void observe(NonNull LifecycleOwner owner, NonNull Observer observer) {mObservers.put((ObserverT) observer, true);super.observe(owner, observer);}Overridepublic void removeObserver(NonNull Observer observer) {mObservers.remove(observer);super.removeObserver(observer);}Overridepublic void removeObservers(NonNull LifecycleOwner owner) {mObservers.clear();super.removeObservers(owner);}public void setValue(Object value) {for (Map.EntryObserverT, Boolean entry : mObservers.entrySet()) {if (entry.getValue()) {entry.setValue(false);entry.getKey().onChanged((T) value);}}}public void call() {setValue(null);}
}2.简单使用
private LiveDataHelperString mLiveDataHelper new LiveDataHelper();Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);initView();initData();initTime();}private void initView() {tvName findViewById(R.id.textview);tvTime findViewById(R.id.tvTime);}private void initData() {mLiveDataHelper.observe(this, new ObserverString() {Overridepublic void onChanged(String name) {Log.d(LiveDataDemo, onChanged: name);}});tvName.setOnClickListener(new View.OnClickListener() {Overridepublic void onClick(View view) {String newName NewName new Random().nextInt(100);mLiveDataHelper.setValue(newName);Log.d(LiveDataDemo, onClick: newName);tvName.setText(String.format(名称发生变化%s, newName));}});}3.布局代码
?xml version1.0 encodingutf-8?
androidx.constraintlayout.widget.ConstraintLayout xmlns:androidhttp://schemas.android.com/apk/res/androidxmlns:apphttp://schemas.android.com/apk/res-autoxmlns:toolshttp://schemas.android.com/toolsandroid:layout_widthmatch_parentandroid:layout_heightmatch_parenttools:context.MainActivityTextViewandroid:idid/textviewandroid:layout_width200dpandroid:layout_height60dpandroid:textHello World!android:backgroundcolor/design_default_color_primaryandroid:textSize20spandroid:textColorcolor/whiteandroid:focusabletrueandroid:gravitycenterapp:layout_constraintBottom_toBottomOfparentapp:layout_constraintEnd_toEndOfparentapp:layout_constraintStart_toStartOfparentapp:layout_constraintTop_toTopOfparent /TextViewandroid:idid/tvTimeandroid:layout_width200dpandroid:layout_height60dpandroid:backgroundcolor/design_default_color_primaryandroid:texttimerandroid:textSize20spandroid:textColorcolor/whiteandroid:focusabletrueandroid:gravitycenterapp:layout_constraintEnd_toEndOfparentapp:layout_constraintStart_toStartOfparentapp:layout_constraintTop_toBottomOfid/textviewandroid:layout_marginTop20dp//androidx.constraintlayout.widget.ConstraintLayout4.实现效果如下 5.封装一个倒计时工具类
package com.example.livedatautilsdemo.helper;import android.os.CountDownTimer;import androidx.lifecycle.MutableLiveData;/*** author: njb* date: 2023/8/6 23:37* desc:*/
public class LiveDataTimeHelper extends MutableLiveDataLong {private CountDownTimer countDownTimer;public void startCountDown(long millisInFuture, long countDownInterval) {countDownTimer new CountDownTimer(millisInFuture, countDownInterval) {Overridepublic void onTick(long millisUntilFinished) {setValue(millisUntilFinished / 1000);}Overridepublic void onFinish() {setValue(0L);}};countDownTimer.start();}public void stopCountDown() {if (countDownTimer ! null) {countDownTimer.cancel();}}Overrideprotected void onInactive() {super.onInactive();stopCountDown();}
}6.倒计时Viewmodel:
package com.example.livedatautilsdemo.viewmodel;import android.os.Handler;
import android.os.Looper;
import android.util.Log;import androidx.lifecycle.LiveData;
import androidx.lifecycle.ViewModel;import com.example.livedatautilsdemo.helper.LiveDataHelper;
import com.example.livedatautilsdemo.helper.LiveDataTimeHelper;import java.util.Timer;
import java.util.TimerTask;/*** author: njb* date: 2023/8/2 23:40* desc:*/
public class TimerLiveDataViewModel extends ViewModel {private LiveDataTimeHelper liveDataHelper;public LiveDataTimeHelper getCurrentSecondLiveData() {if (liveDataHelper null) {liveDataHelper new LiveDataTimeHelper();}return liveDataHelper;}public void startTiming(int seconds) {if (liveDataHelper ! null) {liveDataHelper.startCountDown(seconds * 1000, 1000);}}public void stopTiming() {if (liveDataHelper ! null) {liveDataHelper.stopCountDown();}}Overrideprotected void onCleared() {super.onCleared();stopTiming();}
}7.简单使用
package com.example.livedatautilsdemo.viewmodel;import android.os.Handler;
import android.os.Looper;
import android.util.Log;import androidx.lifecycle.LiveData;
import androidx.lifecycle.ViewModel;import com.example.livedatautilsdemo.helper.LiveDataHelper;
import com.example.livedatautilsdemo.helper.LiveDataTimeHelper;import java.util.Timer;
import java.util.TimerTask;/*** author: njb* date: 2023/8/2 23:40* desc:*/
public class TimerLiveDataViewModel extends ViewModel {private LiveDataTimeHelper liveDataHelper;public LiveDataTimeHelper getCurrentSecondLiveData() {if (liveDataHelper null) {liveDataHelper new LiveDataTimeHelper();}return liveDataHelper;}public void startTiming(int seconds) {if (liveDataHelper ! null) {liveDataHelper.startCountDown(seconds * 1000, 1000);}}public void stopTiming() {if (liveDataHelper ! null) {liveDataHelper.stopCountDown();}}Overrideprotected void onCleared() {super.onCleared();stopTiming();}
}8.实现效果如下 9.项目源码如下
https://gitee.com/jackning_admin/live-data-utils-demo
