use AndroidX.

Author: rome753

activitytaskview/build.gradle

@@ -2,7 +2,6 @@ apply plugin: 'com.android.application'
 
 android {
     compileSdkVersion 28
-    buildToolsVersion "26.0.3"
     defaultConfig {
         applicationId "cc.rome753.activitytask"
         minSdkVersion 15
@@ -24,9 +23,9 @@ android {
 
 dependencies {
     api fileTree(include: ['*.jar'], dir: 'libs')
-    androidTestApi('com.android.support.test.espresso:espresso-core:2.2.2', {
-        exclude group: 'com.android.support', module: 'support-annotations'
-    })
-    api 'com.android.support:appcompat-v7:28.0.0'
-    testApi 'junit:junit:4.12'
+    implementation 'androidx.appcompat:appcompat:1.1.0'
+    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
+    testImplementation 'junit:junit:4.12'
+    androidTestImplementation 'androidx.test:runner:1.2.0'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
 }

app/build.gradle

@@ -2,7 +2,6 @@ apply plugin: 'com.android.application'
 
 android {
     compileSdkVersion 28
-    buildToolsVersion "26.0.3"
     defaultConfig {
         applicationId "cc.rome753.activitytask.demo"
         minSdkVersion 15
@@ -24,9 +23,9 @@ android {
 
 dependencies {
     api fileTree(include: ['*.jar'], dir: 'libs')
-    androidTestApi('com.android.support.test.espresso:espresso-core:2.2.2', {
-        exclude group: 'com.android.support', module: 'support-annotations'
-    })
-    api 'com.android.support:appcompat-v7:28.0.0'
-    testApi 'junit:junit:4.12'
+    implementation 'androidx.appcompat:appcompat:1.1.0'
+    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
+    testImplementation 'junit:junit:4.12'
+    androidTestImplementation 'androidx.test:runner:1.2.0'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
 }

singleinstancedemo/build.gradle

@@ -2,7 +2,6 @@ apply plugin: 'com.android.application'
 
 android {
     compileSdkVersion 28
-    buildToolsVersion "26.0.3"
     defaultConfig {
         applicationId "cc.rome753.singleinstancedemo"
         minSdkVersion 15
@@ -24,9 +23,9 @@ android {
 
 dependencies {
     api fileTree(include: ['*.jar'], dir: 'libs')
-    androidTestApi('com.android.support.test.espresso:espresso-core:2.2.2', {
-        exclude group: 'com.android.support', module: 'support-annotations'
-    })
-    api 'com.android.support:appcompat-v7:28.0.0'
-    testApi 'junit:junit:4.12'
+    implementation 'androidx.appcompat:appcompat:1.1.0'
+    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
+    testImplementation 'junit:junit:4.12'
+    androidTestImplementation 'androidx.test:runner:1.2.0'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
 }