add login values check.

update Chinese translate.

app/src/main/java/net/schueller/peertube/activity/LoginActivity.java

@@ -103,6 +103,15 @@ public class LoginActivity extends CommonActivity {
         String email = mEmailView.getText().toString();
         String password = mPasswordView.getText().toString();
 
+        //check values
+        if (email.isEmpty()) {
+            Toast.makeText(LoginActivity.this, "Email/Username is empty", Toast.LENGTH_LONG).show();
+            return;
+        }
+        if (password.isEmpty()) {
+            Toast.makeText(LoginActivity.this, "Password is empty", Toast.LENGTH_LONG).show();
+            return;
+        }
         // make http call to login and save access tokens
 
         String apiBaseURL = APIUrlHelper.getUrlWithVersion(this);

app/src/main/res/values-zh-rCN/strings.xml

@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-    <string name="app_name">PeerTube</string>
     <string name="action_sign_in_short">登录</string>
     <string name="action_sign_in">登录</string>
     <string name="title_activity_login">登录</string>
@@ -16,8 +15,8 @@
     <string name="pref_title_peertube_server">PeerTube 服务器</string>
     <string name="pref_title_show_nsfw">显示NSFW</string>
     <string name="pref_title_version">版本</string>
-    <string name="prompt_email">邮箱</string>
-    <string name="prompt_password">密码（可选）</string>
+    <string name="prompt_email">邮箱/用户名</string>
+    <string name="prompt_password">密码</string>
     <string name="search_hint">建议</string>
     <string name="title_activity_search">搜索</string>
     <string name="video_speed_10">正常</string>