update MainActivity

app/src/main/AndroidManifest.xml

@@ -14,7 +14,7 @@
         android:theme="@style/Theme.WordBook"
         tools:targetApi="31">
         <activity
-            android:name=".MainActivity"
+            android:name=".main.MainActivity"
             android:exported="true">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

app/src/main/java/com/example/wordbook/StudyActivity.kt

@@ -6,6 +6,6 @@ import android.os.Bundle
 class StudyActivity : AppCompatActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        setContentView(R.layout.activity_main)
+        setContentView(R.layout.activity_study)
     }
 }

app/src/main/java/com/example/wordbook/TestActivity.kt

@@ -6,6 +6,6 @@ import android.os.Bundle
 class TestActivity : AppCompatActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        setContentView(R.layout.activity_main)
+        setContentView(R.layout.activity_test)
     }
 }

app/src/main/java/com/example/wordbook/VocaListActivity.kt

@@ -6,6 +6,6 @@ import android.os.Bundle
 class VocaListActivity : AppCompatActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        setContentView(R.layout.activity_main)
+        setContentView(R.layout.activity_voca_list)
     }
 }

app/src/main/java/com/example/wordbook/main/MainActivity.kt

@@ -0,0 +1,43 @@
+package com.example.wordbook.main
+
+import android.content.Intent
+import androidx.appcompat.app.AppCompatActivity
+import android.os.Bundle
+import androidx.databinding.DataBindingUtil
+import androidx.lifecycle.ViewModelProvider
+import com.example.wordbook.R
+import com.example.wordbook.StudyActivity
+import com.example.wordbook.TestActivity
+import com.example.wordbook.VocaListActivity
+import com.example.wordbook.databinding.ActivityMainBinding
+
+class MainActivity : AppCompatActivity() {
+    private lateinit var mBinding: ActivityMainBinding
+    private lateinit var mViewModel: MainViewModel
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        mBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)
+        mViewModel = ViewModelProvider(this).get(MainViewModel::class.java)
+
+        mBinding.viewModel = mViewModel
+
+        mViewModel.mMoveToStudy.observe(this) {
+            if (it) {
+                startActivity(Intent(this, StudyActivity::class.java))
+            }
+        }
+
+        mViewModel.mMoveToTest.observe(this) {
+            if (it) {
+                startActivity(Intent(this, TestActivity::class.java))
+            }
+        }
+
+        mViewModel.mMoveToVocaList.observe(this) {
+            if (it) {
+                startActivity(Intent(this, VocaListActivity::class.java))
+            }
+        }
+    }
+}

app/src/main/java/com/example/wordbook/main/MainViewModel.kt

@@ -0,0 +1,38 @@
+package com.example.wordbook.main
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.ViewModel
+
+class MainViewModel: ViewModel() {
+    private val _mMoveToStudy = MutableLiveData<Boolean>()
+    val mMoveToStudy: LiveData<Boolean>
+        get() = _mMoveToStudy
+
+    private val _mMoveToTest = MutableLiveData<Boolean>()
+    val mMoveToTest: LiveData<Boolean>
+        get() = _mMoveToTest
+
+    private val _mMoveToVocaList= MutableLiveData<Boolean>()
+    val mMoveToVocaList: LiveData<Boolean>
+        get() = _mMoveToVocaList
+
+    init {
+        _mMoveToStudy.value = false
+        _mMoveToTest.value = false
+        _mMoveToVocaList.value = false
+    }
+
+
+    fun moveToStudy() {
+        _mMoveToStudy.value = true
+    }
+
+    fun moveToTest() {
+        _mMoveToTest.value = true
+    }
+
+    fun moveToVocaList() {
+        _mMoveToVocaList.value = true
+    }
+}

app/src/main/res/layout/activity_main.xml

@@ -2,6 +2,12 @@
 <layout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto">
 
+    <data>
+        <variable
+            name="viewModel"
+            type="com.example.wordbook.main.MainViewModel" />
+    </data>
+
     <androidx.constraintlayout.widget.ConstraintLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
@@ -27,6 +33,7 @@
             android:layout_marginTop="100dp"
             android:layout_marginBottom="20dp"
             android:background="@color/black"
+            android:onClick="@{() -> viewModel.moveToStudy()}"
             android:text="@string/action_study"
             android:textColor="@color/white"
             app:layout_constraintLeft_toLeftOf="parent"
@@ -39,6 +46,7 @@
             android:layout_height="wrap_content"
             android:layout_marginTop="20dp"
             android:background="@color/black"
+            android:onClick="@{() -> viewModel.moveToTest()}"
             android:text="@string/action_test"
             android:textColor="@color/white"
             app:layout_constraintLeft_toLeftOf="parent"
@@ -51,6 +59,7 @@
             android:layout_height="wrap_content"
             android:layout_marginTop="20dp"
             android:background="@color/black"
+            android:onClick="@{() -> viewModel.moveToVocaList()}"
             android:text="@string/action_register"
             android:textColor="@color/white"
             app:layout_constraintLeft_toLeftOf="parent"