Fix executing observable transformation on wrong scheduler.

Author: android10

app/src/main/java/com/fernandocejas/android10/rx/sample/activity/SampleActivityObservableTransfor.java

@@ -10,6 +10,7 @@
 import android.os.Bundle;
 import android.util.Log;
 import android.widget.Button;
+import android.widget.TextView;
 import android.widget.Toast;
 import butterknife.ButterKnife;
 import butterknife.InjectView;
@@ -27,6 +28,11 @@ public class SampleActivityObservableTransfor extends Activity {
 
   private static final String LOG_TAG = "SampleActivityObservableTransfor";
 
+  private static final String SEPARATOR = " ";
+
+  @InjectView(R.id.tv_streamOriginalOrder) TextView tv_streamOriginalOrder;
+  @InjectView(R.id.tv_flatMapResult) TextView tv_flatMapResult;
+  @InjectView(R.id.tv_concatMapResult) TextView tv_concatMapResult;
   @InjectView(R.id.btn_flatMap) Button btn_flatMap;
   @InjectView(R.id.btn_concatMap) Button btn_concatMap;
 
@@ -52,6 +58,7 @@ protected void onCreate(Bundle savedInstanceState) {
 
     ButterKnife.inject(this);
     initialize();
+    populateData();
   }
 
   @Override
@@ -66,12 +73,12 @@ private void initialize() {
   }
 
   @OnClick(R.id.btn_flatMap) void onFlatMapClick() {
-    this.buildNumbersObservable().flatMap(SQUARE_OF_NUMBER).subscribe(new Observer<Integer>() {
-      final StringBuilder stringBuilder = new StringBuilder(10);
+    final Observer<Integer> observer = new Observer<Integer>() {
+      final StringBuilder stringBuilder = new StringBuilder(40);
 
       @Override public void onNext(Integer number) {
         stringBuilder.append(number);
-        stringBuilder.append(Character.SPACE_SEPARATOR);
+        stringBuilder.append(SEPARATOR);
         debugLog("onFlatMapClick() ------>>>> " + number);
       }
 
@@ -84,16 +91,19 @@ private void initialize() {
       @Override public void onError(Throwable e) {
         // handle the exception
       }
-    });
+    };
+
+    this.buildNumbersObservable().flatMap(SQUARE_OF_NUMBER)
+        .observeOn(AndroidSchedulers.mainThread()).subscribe(observer);
   }
 
   @OnClick(R.id.btn_concatMap) void onConcatMapClick() {
-    this.buildNumbersObservable().concatMap(SQUARE_OF_NUMBER).subscribe(new Observer<Integer>() {
-      final StringBuilder stringBuilder = new StringBuilder(10);
+    final Observer<Integer> observer = new Observer<Integer>() {
+      final StringBuilder stringBuilder = new StringBuilder(40);
 
       @Override public void onNext(Integer number) {
         stringBuilder.append(number);
-        stringBuilder.append(Character.SPACE_SEPARATOR);
+        stringBuilder.append(SEPARATOR);
         debugLog("onConcatMapClick() ------>>>> " + number);
       }
 
@@ -106,11 +116,14 @@ private void initialize() {
       @Override public void onError(Throwable e) {
         // handle the exception
       }
-    });
+    };
+
+    this.buildNumbersObservable().concatMap(SQUARE_OF_NUMBER)
+        .observeOn(AndroidSchedulers.mainThread()).subscribe(observer);
   }
 
   private Observable<Integer> buildNumbersObservable() {
-    return this.dataManager.getNumbers().subscribeOn(AndroidSchedulers.mainThread());
+    return this.dataManager.getNumbers();
   }
 
   private void showToast(String message) {
@@ -121,11 +134,20 @@ private void debugLog(String message) {
     Log.d(LOG_TAG, message);
   }
 
-  private void printConcatMapResult(String result) {
-
+  private void printFlatMapResult(String result) {
+    this.tv_flatMapResult.setText(result);
   }
 
-  private void printFlatMapResult(String result) {
+  private void printConcatMapResult(String result) {
+    this.tv_concatMapResult.setText(result);
+  }
 
+  private void populateData() {
+    StringBuilder stringBuilder = new StringBuilder(15);
+    for (int number : dataManager.getNumbersSync()) {
+      stringBuilder.append(number);
+      stringBuilder.append(SEPARATOR);
+    }
+    this.tv_streamOriginalOrder.setText(stringBuilder.toString());
   }
 }

app/src/main/java/com/fernandocejas/android10/rx/sample/data/DataManager.java

@@ -33,6 +33,10 @@ public Observable<Integer> getNumbers() {
     return Observable.from(numbers);
   }
 
+  public List<Integer> getNumbersSync() {
+    return this.numbers;
+  }
+
   public Observable<Integer> squareOf(int number) {
     return Observable.just(number * number).subscribeOn(Schedulers.from(this.jobExecutor));
   }

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

@@ -34,12 +34,28 @@
   </RelativeLayout>
 
   <LinearLayout
-      android:layout_width="wrap_content"
-      android:layout_height="wrap_content"
+      android:layout_width="match_parent"
+      android:layout_height="match_parent"
       android:orientation="vertical"
       android:layout_above="@id/rl_buttonsHolder"
       >
 
+    <TextView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="@string/string_sample_observable_transformation"
+        />
+
+    <TextView
+        style="@style/AppTheme.TextViewTitle"
+        android:text="@string/tv_label_original_order"
+        />
+    <TextView
+        android:id="@+id/tv_streamOriginalOrder"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        />
+
     <TextView
         style="@style/AppTheme.TextViewTitle"
         android:text="@string/tv_label_flatMap_result"

app/src/main/res/values/strings.xml

@@ -14,9 +14,11 @@
   <string name="btn_text_concat_map">Observable.concatMap()</string>
   <string name="btn_text_add_element">Add Element</string>
 
+  <string name="tv_label_original_order">Original stream order:</string>
   <string name="tv_label_flatMap_result">flatMap() Result:</string>
   <string name="tv_label_concatMap_result">concatMap() Result:</string>
 
   <string name="string_content_description">Non accessible view</string>
+  <string name="string_sample_observable_transformation">This sample demonstrates an observable transformation by applying a function (square of a number) to a set of values. The basic idea is to see the difference between both flatMap() and concatMap() methods whereas one take care of the order and the other does not.</string>
 
 </resources>