feat: 在 choose area 界面按返回按钮时，逐级返回，而不是直接退出 app

app/src/main/java/com/coolweather/android/ChooseAreaFragment.java

@@ -4,7 +4,6 @@
 import android.content.Intent;
 import android.os.Bundle;
 import android.support.v4.app.Fragment;
-import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -272,4 +271,24 @@ private void closeProgressDialog() {
         }
     }
 
+    /**
+     * 托管此 fragment 的 activity 可以调用此方法, 以便给此 fragment 一个处理点击返回按钮的机会
+     * @return true 表示此 fragment 处理了点击返回按钮的事件, activity 可以不处理了, false 表示 fragment 不处理
+     */
+    public boolean onBackPressed() {
+        if (currentLevel == LEVEL_COUNTY) {
+            currentLevel = LEVEL_CITY;
+            queryCities();
+        } else if (currentLevel == LEVEL_CITY) {
+            currentLevel = LEVEL_PROVINCE;
+            queryProvinces();
+        } else {
+            return false;
+        }
+        return true;
+    }
+
+    public int getCurrentLevel() {
+        return currentLevel;
+    }
 }

app/src/main/java/com/coolweather/android/MainActivity.java

@@ -3,16 +3,26 @@
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.preference.PreferenceManager;
-import android.support.v7.app.ActionBar;
+import android.support.v4.app.FragmentManager;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 
 public class MainActivity extends AppCompatActivity {
+    ChooseAreaFragment mFragment;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
+
+        // 通过代码来托管 fragment
+        FragmentManager fm = getSupportFragmentManager();
+        mFragment = (ChooseAreaFragment) fm.findFragmentById(R.id.fragment_container);
+        if (mFragment == null) {
+            mFragment = new ChooseAreaFragment();
+            fm.beginTransaction().add(R.id.fragment_container, mFragment).commit();
+        }
+
         SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
         if (prefs.getString("weather", null) != null) {
             Intent intent = new Intent(this, WeatherActivity.class);
@@ -21,4 +31,10 @@ protected void onCreate(Bundle savedInstanceState) {
         }
     }
 
+    @Override
+    public void onBackPressed() {
+        if (!mFragment.onBackPressed()) {
+            super.onBackPressed();
+        }
+    }
 }

app/src/main/java/com/coolweather/android/WeatherActivity.java

@@ -6,6 +6,7 @@
 import android.os.Build;
 import android.os.Bundle;
 import android.preference.PreferenceManager;
+import android.support.v4.app.FragmentManager;
 import android.support.v4.view.GravityCompat;
 import android.support.v4.widget.DrawerLayout;
 import android.support.v4.widget.SwipeRefreshLayout;
@@ -66,6 +67,8 @@ public class WeatherActivity extends AppCompatActivity {
 
     private String mWeatherId;
 
+    private ChooseAreaFragment chooseAreaFragment;
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -106,6 +109,15 @@ protected void onCreate(Bundle savedInstanceState) {
             weatherLayout.setVisibility(View.INVISIBLE);
             requestWeather(mWeatherId);
         }
+
+        // 通过代码来托管 fragment
+        FragmentManager fm = getSupportFragmentManager();
+        chooseAreaFragment = (ChooseAreaFragment) fm.findFragmentById(R.id.fragment_container);
+        if (chooseAreaFragment == null) {
+            chooseAreaFragment = new ChooseAreaFragment();
+            fm.beginTransaction().add(R.id.fragment_container, chooseAreaFragment).commit();
+        }
+
         swipeRefresh.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
             @Override
             public void onRefresh() {
@@ -235,4 +247,19 @@ private void showWeatherInfo(Weather weather) {
         startService(intent);
     }
 
+    @Override
+    public void onBackPressed() {
+        if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
+            if (chooseAreaFragment.getCurrentLevel() == ChooseAreaFragment.LEVEL_PROVINCE) {
+                // 在 choose area 时如果是省一级的, 点击返回时关闭 drawer 视图
+                drawerLayout.closeDrawers();
+            } else {
+                // 如果是市或者区一级的, 就让 fragment 处理点击返回按钮事件, 即返回更大一级的 choose area 界面
+                chooseAreaFragment.onBackPressed();
+            }
+        } else {
+            // drawer 未显示, 则直接退出 app
+            super.onBackPressed();
+        }
+    }
 }

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

@@ -1,13 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <FrameLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/fragment_container"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
-
-    <fragment
-        android:id="@+id/choose_area_fragment"
-        android:name="com.coolweather.android.ChooseAreaFragment"
-        android:layout_width="match_parent"
-        android:layout_height="match_parent" />
-
 </FrameLayout>

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

@@ -50,13 +50,13 @@
 
         </android.support.v4.widget.SwipeRefreshLayout>
 
-        <fragment
-            android:id="@+id/choose_area_fragment"
-            android:name="com.coolweather.android.ChooseAreaFragment"
-            android:layout_width="match_parent"
-            android:layout_height="match_parent"
+        <FrameLayout
+            xmlns:android="http://schemas.android.com/apk/res/android"
+            android:id="@+id/fragment_container"
             android:layout_gravity="start"
-            />
+            android:layout_width="match_parent"
+            android:layout_height="match_parent">
+        </FrameLayout>
 
     </android.support.v4.widget.DrawerLayout>