Android通过ViewModel保存数据实现多页面的数据共享功能

通过viewmodel实现的数据共享符合android的mvc设计模式，将数据独立出来

实现的demo

1、主页面通过seekbar 来改变数字的值

2、点击进入就进入第二个界面，但是数据还是共享的

3、随便加两个数字上去，再次切换

4、发现数据还是共享的

下面是具体实现步骤：

1、建立两个fragment（使用了binding 和 navigation）

一点要添加binding 和 navigation 不然做不了

2、建立一个继承于viewmodel的类

3、分别在两个fragment的代码中使用继承于viewmodel的那个类，就可以实现数据共享

下面是具体代码：

1、继承于viewmodel的类

package com.example.naviation01;
import androidx.lifecycle.mutablelivedata;
import androidx.lifecycle.viewmodel;
public class myviewmode extends viewmodel {
  private mutablelivedata<integer> number;
  public mutablelivedata<integer> getnumber(){
    if(this.number == null){
      this.number = new mutablelivedata<>();
      this.number.setvalue(0);
    }
    return this.number;
  }
  public void add(int x){
    this.number.setvalue(this.number.getvalue()+x);
    if(this.number.getvalue() < 0){
      this.number.setvalue(0);
    }
  }
}

2、fragment 主页

package com.example.naviation01;
import android.os.bundle;
import androidx.databinding.databindingutil;
import androidx.fragment.app.fragment;
import androidx.fragment.app.fragmentcontroller;
import androidx.lifecycle.viewmodel;
import androidx.lifecycle.viewmodelprovider;
import androidx.lifecycle.viewmodelproviders;
import androidx.navigation.navcontroller;
import androidx.navigation.navigation;
import android.view.layoutinflater;
import android.view.view;
import android.view.viewgroup;
import android.widget.seekbar;
import com.example.naviation01.databinding.fragmenthomebinding;
/**
 * a simple {@link fragment} subclass.
 */
public class homefragment extends fragment {
  public homefragment() {
    // required empty public constructor
  }
  @override
  public view oncreateview(layoutinflater inflater, viewgroup container,
               bundle savedinstancestate) {
    // inflate the layout for this fragment
    final myviewmode myviewmode;
    myviewmode = viewmodelproviders.of(getactivity()).get(myviewmode.class);
    fragmenthomebinding binding;
    binding = databindingutil.inflate(inflater,r.layout.fragment_home,container,false);
    binding.setdata(myviewmode);
    binding.setlifecycleowner(getactivity());
    binding.seekbar.setprogress(myviewmode.getnumber().getvalue());
    binding.seekbar.setonseekbarchangelistener(new seekbar.onseekbarchangelistener() {
      @override
      public void onprogresschanged(seekbar seekbar, int progress, boolean fromuser) {
        myviewmode.getnumber().setvalue(progress);
      }
      @override
      public void onstarttrackingtouch(seekbar seekbar) {
      }
      @override
      public void onstoptrackingtouch(seekbar seekbar) {
      }
    });
    binding.button.setonclicklistener(new view.onclicklistener() {
      @override
      public void onclick(view v) {
        navcontroller controller = navigation.findnavcontroller(v);
        controller.navigate(r.id.action_homefragment_to_detailfragment);
      }
    });
    return binding.getroot();
    //return inflater.inflate(r.layout.fragment_home, container, false);
  }
}

xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools">
  <data>
    <variable
      name="data"
      type="com.example.naviation01.myviewmode" />
  </data>
  <framelayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".homefragment">
    <androidx.constraintlayout.widget.constraintlayout
      android:layout_width="match_parent"
      android:layout_height="match_parent">
      <textview
        android:id="@+id/textview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginstart="8dp"
        android:layout_marginend="8dp"
        android:layout_marginbottom="8dp"
        android:text="@{string.valueof(data.number)}"
        android:textsize="30sp"
        app:layout_constraintbottom_tobottomof="parent"
        app:layout_constraintend_toendof="parent"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent"
        app:layout_constraintvertical_bias="0.255" />
      <seekbar
        android:id="@+id/seekbar"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginstart="8dp"
        android:layout_margintop="8dp"
        android:layout_marginend="8dp"
        android:layout_marginbottom="8dp"
        app:layout_constraintbottom_tobottomof="parent"
        app:layout_constraintend_toendof="parent"
        app:layout_constrainthorizontal_bias="0.0"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent"
        app:layout_constraintvertical_bias="0.456" />
      <button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginstart="8dp"
        android:layout_margintop="8dp"
        android:layout_marginend="8dp"
        android:layout_marginbottom="8dp"
        android:text="@string/function01"
        app:layout_constraintbottom_tobottomof="parent"
        app:layout_constraintend_toendof="parent"
        app:layout_constrainthorizontal_bias="0.498"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent"
        app:layout_constraintvertical_bias="0.679" />
    </androidx.constraintlayout.widget.constraintlayout>
  </framelayout>
</layout>

3、fragment 副页

package com.example.naviation01;
import android.os.bundle;
import androidx.databinding.databindingutil;
import androidx.fragment.app.fragment;
import androidx.lifecycle.viewmodelproviders;
import androidx.navigation.navcontroller;
import androidx.navigation.navigation;
import android.view.layoutinflater;
import android.view.view;
import android.view.viewgroup;
import com.example.naviation01.databinding.fragmentdetailbinding;
/**
 * a simple {@link fragment} subclass.
 */
public class detailfragment extends fragment {
  public detailfragment() {
    // required empty public constructor
  }
  @override
  public view oncreateview(layoutinflater inflater, viewgroup container,
               bundle savedinstancestate) {
    // inflate the layout for this fragment
    myviewmode myviewmode;
    myviewmode = viewmodelproviders.of(getactivity()).get(myviewmode.class);
    fragmentdetailbinding binding;
    binding = databindingutil.inflate(inflater,r.layout.fragment_detail,container,false);
    binding.setdate(myviewmode);
    binding.setlifecycleowner(getactivity());
    binding.button4.setonclicklistener(new view.onclicklistener() {
      @override
      public void onclick(view v) {
        navcontroller controller = navigation.findnavcontroller(v);
        controller.navigate(r.id.action_detailfragment_to_homefragment);
      }
    });
    return binding.getroot();
    //return inflater.inflate(r.layout.fragment_detail, container, false);
  }
}

xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools">
  <data>
    <variable
      name="date"
      type="com.example.naviation01.myviewmode" />
  </data>
  <framelayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".detailfragment">
    <androidx.constraintlayout.widget.constraintlayout
      android:layout_width="match_parent"
      android:layout_height="match_parent">
      <textview
        android:id="@+id/textview3"
        android:layout_width="131dp"
        android:layout_height="55dp"
        android:layout_marginstart="8dp"
        android:layout_margintop="8dp"
        android:layout_marginend="8dp"
        android:layout_marginbottom="8dp"
        android:text="@{string.valueof(date.number)}"
        android:textsize="30sp"
        app:layout_constraintbottom_tobottomof="parent"
        app:layout_constraintend_toendof="parent"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent"
        app:layout_constraintvertical_bias="0.23" />
      <button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginstart="8dp"
        android:layout_margintop="8dp"
        android:layout_marginend="8dp"
        android:layout_marginbottom="8dp"
        android:text="@string/function02"
        android:onclick="@{()->date.add(1)}"
        app:layout_constraintbottom_tobottomof="parent"
        app:layout_constraintend_toendof="parent"
        app:layout_constrainthorizontal_bias="0.104"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent"
        app:layout_constraintvertical_bias="0.499" />
      <button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginstart="8dp"
        android:layout_margintop="8dp"
        android:layout_marginend="8dp"
        android:layout_marginbottom="8dp"
        android:text="@string/function03"
        android:onclick="@{()->date.add(-1)}"
        app:layout_constraintbottom_tobottomof="parent"
        app:layout_constraintend_toendof="parent"
        app:layout_constrainthorizontal_bias="0.899"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent"
        app:layout_constraintvertical_bias="0.499" />
      <button
        android:id="@+id/button4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginstart="8dp"
        android:layout_margintop="8dp"
        android:layout_marginend="8dp"
        android:layout_marginbottom="8dp"
        android:text="@string/function04"
        app:layout_constraintbottom_tobottomof="parent"
        app:layout_constraintend_toendof="parent"
        app:layout_constrainthorizontal_bias="0.498"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent"
        app:layout_constraintvertical_bias="0.664" />
    </androidx.constraintlayout.widget.constraintlayout>
  </framelayout>
</layout>

4、xml main_activity

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.constraintlayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context=".mainactivity">
  <fragment
    android:id="@+id/fragment"
    android:name="androidx.navigation.fragment.navhostfragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margintop="8dp"
    android:layout_marginend="8dp"
    android:layout_marginbottom="8dp"
    app:defaultnavhost="true"
    app:layout_constraintbottom_tobottomof="parent"
    app:layout_constraintend_toendof="parent"
    app:layout_constraintstart_tostartof="parent"
    app:layout_constrainttop_totopof="parent"
    app:navgraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.constraintlayout>

总结

以上所述是小编给大家介绍的android通过viewmodel保存数据实现多页面的数据共享功能，希望对大家有所帮助