Android學習筆記——UI基礎之編寫介面最佳實踐
阿新 • • 發佈:2019-01-02
參考書籍:Android第一行程式碼(第二版).郭霖著
1、製作Nine-Patch圖片
一種被特殊處理過的png圖片,能夠指定那些區域可以被拉伸、哪些不可以。在Android sdk目錄下有一個tools資料夾,找到draw9patch.bat檔案來製作Nine-Patch圖片(要開啟此檔案需將JDK的bin目錄配置到環境變數中,如使用的AS內建jdk,則要配置的路徑是Android Studio安裝目錄/jre/bin).
由於Android Studio已內建此功能,所以只需將圖片匯入專案後點擊滑鼠右鍵->Create 9-Patch file…然後確認路徑名稱即可。
2、編寫精美聊天介面
需要準備接收和傳送訊息背景圖(nine-patch),使用RecyclerView控制元件,所以要在build.gradle中新增相應依賴庫
compile ‘com.android.support:recyclerview-v7:24.2.1’
編寫主介面,修改佈局檔案:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/msg_recycler_view"
android:layout_width ="match_parent"
android:layout_height="0dp"
android:layout_weight="1"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<EditText
android:id="@+id/input_text"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:hint="Type something here"
android:maxLines="2"/>
<Button
android:id="@+id/send"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Send"/>
</LinearLayout>
</LinearLayout>
中間顯示聊天訊息內容,底部為文字輸入框和傳送按鈕。
然後定義訊息實體類:
public class Msg {
public static final int TYPE_RECEIVED = 0;
public static final int TYPE_SENT = 1;
private String content;
private int type;
public Msg(String content, int type){
this.content = content;
this.type = type;
}
public String getContent() {
return content;
}
public int getType() {
return type;
}
}
content表示訊息內容,type表示訊息型別(兩個值可選:TYPE_RECEIVED/TYPE_SENT).
編寫RecyclerVeiw子項佈局,新建msg_item.xml如下:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="10dp">
<LinearLayout
android:id="@+id/left_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="left"
android:background="@drawable/message_left">
<TextView
android:id="@+id/left_msg"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="10dp"
android:textColor="#fff"/>
</LinearLayout>
<LinearLayout
android:id="@+id/right_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="right"
android:background="@drawable/message_right">
<TextView
android:id="@+id/right_msg"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="10dp" />
</LinearLayout>
</LinearLayout>
接收訊息居左對齊,傳送訊息居右對齊,分別設定了背景圖。後面通過程式碼來顯示隱藏傳送/接受訊息。
接下來建立RecyclerView的介面卡類,新建類MsgAdapter:
public class MsgAdapter extends RecyclerView.Adapter<MsgAdapter.ViewHolder> {
private List<Msg> mMsgList;
static class ViewHolder extends RecyclerView.ViewHolder{
LinearLayout leftLayout;
LinearLayout rightLayout;
TextView leftMsg;
TextView rightMsg;
public ViewHolder(View itemView) {
super(itemView);
leftLayout = (LinearLayout) itemView.findViewById(R.id.left_layout);
rightLayout = (LinearLayout) itemView.findViewById(R.id.right_layout);
leftMsg = (TextView) itemView.findViewById(R.id.left_msg);
rightMsg = (TextView) itemView.findViewById(R.id.right_msg);
}
}
public MsgAdapter(List<Msg> msgList){
mMsgList = msgList;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.msg_item,parent,false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Msg msg = mMsgList.get(position);
if (msg.getType() == Msg.TYPE_RECEIVED){
//如果是收到的訊息,則顯示左邊的訊息佈局,將右邊的訊息佈局隱藏
holder.leftLayout.setVisibility(View.VISIBLE);
holder.rightLayout.setVisibility(View.GONE);
holder.leftMsg.setText(msg.getContent());
}else if(msg.getType() == Msg.TYPE_SENT){
//如果是發出的訊息,則相反的處理
holder.rightLayout.setVisibility(View.VISIBLE);
holder.leftLayout.setVisibility(View.GONE);
holder.rightMsg.setText(msg.getContent());
}
}
@Override
public int getItemCount() {
return mMsgList.size();
}
}
最後修改MainActivity中的程式碼,初始化資料並給傳送按鈕加入事件響應:
public class MainActivity extends AppCompatActivity {
private List<Msg> msgList = new ArrayList<>();
private EditText inputText;
private Button send;
private RecyclerView msgRecyclerView;
private MsgAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initMsgs();//初始化訊息資料
inputText = (EditText) findViewById(R.id.input_text);
send = (Button) findViewById(R.id.send);
msgRecyclerView = (RecyclerView) findViewById(R.id.msg_recycler_view);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
msgRecyclerView.setLayoutManager(layoutManager);
adapter = new MsgAdapter(msgList);
msgRecyclerView.setAdapter(adapter);
send.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String cotent = inputText.getText().toString();
if (!"".equals(cotent)){
Msg msg = new Msg(cotent,Msg.TYPE_SENT);
msgList.add(msg);
adapter.notifyItemInserted(msgList.size() - 1);//當有新訊息時,重新整理RecyclerView中的顯示
msgRecyclerView.scrollToPosition(msgList.size() - 1);//將RecyclerView定位到最後一行
inputText.setText("");//清空輸入框
}
}
});
}
private void initMsgs(){
Msg msg1 = new Msg("Hello guy." , Msg.TYPE_RECEIVED);
msgList.add(msg1);
Msg msg2 = new Msg("Hello.Who is tha?" , Msg.TYPE_SENT);
msgList.add(msg2);
Msg msg3 = new Msg("This is Tom.Nice talking to you." , Msg.TYPE_RECEIVED);
msgList.add(msg3);
}
}
效果如下: