创建 Contract 类

app/src/main/java/com/example/pets/EditorActivity.java

@@ -28,6 +28,8 @@
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.core.app.NavUtils;
 
+import com.example.pets.data.PetContract.PetEntry;
+
 /**
  * Allows user to create a new pet or edit an existing one.
  */
@@ -54,10 +56,11 @@ public class EditorActivity extends AppCompatActivity {
     private Spinner mGenderSpinner;
 
     /**
-     * Gender of the pet. The possible values are:
-     * 0 for unknown gender, 1 for male, 2 for female.
+     * Gender of the pet. The possible valid values are in the PetContract.java file:
+     * {@link PetEntry#GENDER_UNKNOWN}, {@link PetEntry#GENDER_MALE}, or
+     * {@link PetEntry#GENDER_FEMALE}.
      */
-    private int mGender = 0;
+    private int mGender = PetEntry.GENDER_UNKNOWN;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
@@ -95,11 +98,11 @@ public void onItemSelected(AdapterView<?> parent, View view, int position, long
                 String selection = (String) parent.getItemAtPosition(position);
                 if (!TextUtils.isEmpty(selection)) {
                     if (selection.equals(getString(R.string.gender_male))) {
-                        mGender = 1; // Male
+                        mGender = PetEntry.GENDER_MALE; // Male
                     } else if (selection.equals(getString(R.string.gender_female))) {
-                        mGender = 2; // Female
+                        mGender = PetEntry.GENDER_FEMALE; // Female
                     } else {
-                        mGender = 0; // Unknown
+                        mGender = PetEntry.GENDER_UNKNOWN; // Unknown
                     }
                 }
             }

app/src/main/java/com/example/pets/data/PetContract.java

@@ -0,0 +1,72 @@
+package com.example.pets.data;
+
+import android.provider.BaseColumns;
+
+
+/**
+ * API Contract for the Pets app.
+ */
+public final class PetContract {
+
+    // To prevent someone from accidentally instantiating the contract class,
+    // give it an empty constructor.
+    private PetContract() {
+    }
+
+    /**
+     * Inner class that defines constant values for the pets database table.
+     * Each entry in the table represents a single pet.
+     */
+    public static final class PetEntry implements BaseColumns {
+
+        /**
+         * Name of database table for pets
+         */
+        public final static String TABLE_NAME = "pets";
+
+        /**
+         * Unique ID number for the pet (only for use in the database table).
+         * <p>
+         * Type: INTEGER
+         */
+        public final static String _ID = BaseColumns._ID;
+
+        /**
+         * Name of the pet.
+         * <p>
+         * Type: TEXT
+         */
+        public final static String COLUMN_PET_NAME = "name";
+
+        /**
+         * Breed of the pet.
+         * <p>
+         * Type: TEXT
+         */
+        public final static String COLUMN_PET_BREED = "breed";
+
+        /**
+         * Gender of the pet.
+         * <p>
+         * The only possible values are {@link #GENDER_UNKNOWN}, {@link #GENDER_MALE},
+         * or {@link #GENDER_FEMALE}.
+         * <p>
+         * Type: INTEGER
+         */
+        public final static String COLUMN_PET_GENDER = "gender";
+
+        /**
+         * Weight of the pet.
+         * <p>
+         * Type: INTEGER
+         */
+        public final static String COLUMN_PET_WEIGHT = "weight";
+
+        /**
+         * Possible values for the gender of the pet.
+         */
+        public static final int GENDER_UNKNOWN = 0;
+        public static final int GENDER_MALE = 1;
+        public static final int GENDER_FEMALE = 2;
+    }
+}