fix a crash issue and update sdk version

MPChartExample/build.gradle

@@ -1,11 +1,11 @@
 apply plugin: 'com.android.application'
 
 android {
-    compileSdkVersion 28
+    compileSdkVersion 33
     defaultConfig {
         applicationId "com.xxmassdeveloper.mpchartexample"
-        minSdkVersion 16
-        targetSdkVersion 28
+        minSdkVersion 23
+        targetSdkVersion 33
         versionCode 57
         versionName '3.1.0'
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
@@ -18,7 +18,9 @@ android {
         }
     }
 }
-
+task wrapper(type: Wrapper){
+    gradleVersion = '7.2'
+}
 dependencies {
     implementation "androidx.appcompat:appcompat:1.0.2"
     implementation 'com.google.android.material:material:1.0.0'

MPChartExample/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.2-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

MPChartExample/src/main/AndroidManifest.xml

@@ -12,7 +12,8 @@
         android:theme="@style/AppTheme">
         <activity
             android:name="com.xxmassdeveloper.mpchartexample.notimportant.MainActivity"
-            android:label="@string/app_name" >
+            android:label="@string/app_name"
+            android:exported="true">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <action android:name="android.intent.action.VIEW" />

MPChartLib/build.gradle

@@ -4,11 +4,11 @@ apply plugin: 'com.github.dcendents.android-maven'
 group='com.github.philjay'
 
 android {
-    compileSdkVersion 28
+    compileSdkVersion 33
     buildToolsVersion '28.0.3'
     defaultConfig {
-        minSdkVersion 14
-        targetSdkVersion 28
+        minSdkVersion 23
+        targetSdkVersion 33
         versionCode 3
         versionName '3.1.0'
     }

MPChartLib/src/main/java/com/github/mikephil/charting/charts/Chart.java

@@ -791,6 +791,10 @@ protected void drawMarkers(Canvas canvas) {
             IDataSet set = mData.getDataSetByIndex(highlight.getDataSetIndex());
 
             Entry e = mData.getEntryForHighlight(mIndicesToHighlight[i]);
+
+            if(e==null || set==null)
+                continue;
+
             int entryIndex = set.getEntryIndex(e);
 
             // make sure entry not null

MPChartLib/src/main/java/com/github/mikephil/charting/charts/CombinedChart.java

@@ -246,7 +246,8 @@ protected void drawMarkers(Canvas canvas) {
             IDataSet set = mData.getDataSetByHighlight(highlight);
 
             Entry e = mData.getEntryForHighlight(highlight);
-            if (e == null)
+
+            if(e==null || set==null)
                 continue;
 
             int entryIndex = set.getEntryIndex(e);