Android的ToDoList 詳解

ToDoList是一個Android的入門程式, 包含兩個控制項, EditText(編輯文本),ListView(列表視圖), 放置在LinearLayout(線性布局);

需要重寫監聽按鍵(setOnKeyListener), 使用適配器(Adapter)進行關聯;

1. 主介面(activity_to_do_list.xml)的代碼:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:paddingBottom="@dimen/activity_vertical_margin"    tools:context="mzx.spike.todolist.app.ToDoListActivity">            <EditText        android:id="@+id/myEditText"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="@string/addItemHint"        android:contentDescription="@string/addItemContentDescription"     />            <ListView        android:id="@+id/myListView"        android:layout_width="match_parent"        android:layout_height="wrap_content"     />        </LinearLayout>

位置: res->layout->activity_to_do_list.xml

注意:

1. 所有控制項, 必須要指定layout_width(控制項寬度), layout_height(控制項高度), 兩個屬性, Android系統會做出相應的匹配;

2. id屬性, 是為了在R檔案中註冊, 在程式邏輯(java檔案)中使用, 所以使用"@+id", "+"表示添加的意思;

3. LinearLayout控制項(線性), 需要指明orientation(方向), 使其內部控制項有序排列;

4. layout的匹配常用的兩種屬性: match_parent(匹配父控制項, 填充),wrap_content(包圍內容, 根據內容最小化);

2. 字串(strings.xml)的代碼:

<?xml version="1.0" encoding="utf-8"?>  <resources>            <string name="app_name">ToDoList</string>      <string name="addItemHint">New To Do Item</string>      <string name="addItemContentDescription">New To Do Item</string>      <string name="action_settings">Settings</string>        </resources>

位置: res->values->string.xml

注意:

使用字串的形式, 可以使展示層和應用邏輯層分離, 可以擴充其他語言;

3. 程式邏輯(ToDoListActivity.java)的代碼:

package mzx.spike.todolist.app;        import android.os.Bundle;  import android.support.v7.app.ActionBarActivity;  import android.view.KeyEvent;  import android.view.Menu;  import android.view.MenuItem;  import android.view.View;  import android.widget.ArrayAdapter;  import android.widget.EditText;  import android.widget.ListView;        import java.util.ArrayList;              public class ToDoListActivity extends ActionBarActivity {            @Override    protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_to_do_list);                //擷取對UI組件的引用// 查看本欄目更多精彩內容：http://www.bianceng.cnhttp://www.bianceng.cn/OS/extra/        ListView myListView = (ListView)findViewById(R.id.myListView);          final EditText myEditText = (EditText)findViewById(R.id.myEditText); //final 表示常量                //擷取對UI組件的引用          final ArrayList<String> todoItems = new ArrayList<String>();                //建立ArrayAdapter以便講數組綁定到ListView          final ArrayAdapter<String> aa;          aa = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, todoItems);                //將ArrayAdapter綁定到ListView          myListView.setAdapter(aa);                //監聽myEditText的Enter鍵          myEditText.setOnKeyListener(new View.OnKeyListener() {              @Override            public boolean onKey(View view, int i, KeyEvent keyEvent) {                  if (keyEvent.getAction() == KeyEvent.ACTION_DOWN)                      if ((i == KeyEvent.KEYCODE_DPAD_CENTER) || (i == KeyEvent.KEYCODE_ENTER)) {                          todoItems.add(0, myEditText.getText().toString());                          aa.notifyDataSetChanged();                          myEditText.setText("");                          return true;                      }                  return false;              }          });      }                  @Override    public boolean onCreateOptionsMenu(Menu menu) {                        // Inflate the menu; this adds items to the action bar if it is present.          getMenuInflater().inflate(R.menu.to_do_list, menu);          return true;      }            @Override    public boolean onOptionsItemSelected(MenuItem item) {          // Handle action bar item clicks here. The action bar will          // automatically handle clicks on the Home/Up button, so long          // as you specify a parent activity in AndroidManifest.xml.          int id = item.getItemId();          if (id == R.id.action_settings) {              return true;          }          return super.onOptionsItemSelected(item);      }        }

查看本欄目更多精彩內容：http://www.bianceng.cnhttp://www.bianceng.cn/OS/extra/