功能
下拉框相當常見了,例如選擇省、市、縣;例如選擇部門;選擇員工。用處一般是多選一。
顯示
下拉框一般有兩種形式,一種是下拉顯示可選項,一種是彈窗顯示可選項。通過調整參數spinnerMode,dropdown/dialog分別代表兩種下拉框。
注意下拉框的數據需要從資源中關聯過來,資源文件res/values/arrays.xml
代碼如下:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string-array name="gradeArray">
<item>初一</item>
<item>初二</item>
<item>初三</item>
</string-array>
</resources>
Android佈局文件如下:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="4dp">
<Spinner
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:entries="@array/gradeArray"
android:spinnerMode="dropdown"></Spinner>
<Spinner
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:entries="@array/gradeArray"
android:spinnerMode="dialog"></Spinner>
<Button
android:id="@+id/buttonOk"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="確認" />
</LinearLayout>
效果如下:
動態設置選項
可以利用數組適配器ArrayAdapter
動態設置下來框的選項,佈局文件修改爲:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="4dp">
<Spinner
android:id="@+id/spinnerGrade"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:spinnerMode="dropdown"></Spinner>
<Button
android:id="@+id/buttonOk"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="確認" />
</LinearLayout>
代碼部分修改爲:
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
//內容數組
String[] gradeArray={"初一","初二","初三","初四"};
//數組適配器
ArrayAdapter<String> gradeAdapter=new ArrayAdapter<>(this,R.layout.support_simple_spinner_dropdown_item,gradeArray);
spinnerGrade.setAdapter(gradeAdapter);
//設置默認選中項
spinnerGrade.setSelection(0);
}
}
獲取選中項
點擊確認後獲取選中項,並顯示選中項內容。
public class MainActivity extends AppCompatActivity {
//內容數組
String[] gradeArray={"初一","初二","初三","初四"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
//數組適配器
ArrayAdapter<String> gradeAdapter=new ArrayAdapter<>(this,R.layout.support_simple_spinner_dropdown_item,gradeArray);
spinnerGrade.setAdapter(gradeAdapter);
//設置默認選中項
spinnerGrade.setSelection(0);
//獲取按鈕
Button buttonOk = findViewById(R.id.buttonOk);
//設置按鈕點擊監聽器
buttonOk.setOnClickListener(new MyOnClickListener());
}
//定義按鈕點擊監聽器
class MyOnClickListener implements View.OnClickListener {
//按鈕點擊
@Override
public void onClick(View view) {
if (view.getId() == R.id.buttonOk) {//被點擊的是確認按鈕
//獲取選中項
Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
//顯示提示框
Toast.makeText(MainActivity.this, gradeArray[spinnerGrade.getSelectedItemPosition()] , Toast.LENGTH_SHORT).show();
}
}
}
}
監聽下拉框選中項
當下拉框選中項發生改變時,彈窗顯示新項目,代碼如下:
public class MainActivity extends AppCompatActivity {
//內容數組
String[] gradeArray={"初一","初二","初三","初四"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
//數組適配器
ArrayAdapter<String> gradeAdapter=new ArrayAdapter<>(this,R.layout.support_simple_spinner_dropdown_item,gradeArray);
spinnerGrade.setAdapter(gradeAdapter);
//設置默認選中項
spinnerGrade.setSelection(0);
//獲取按鈕
Button buttonOk = findViewById(R.id.buttonOk);
//設置按鈕點擊監聽器
buttonOk.setOnClickListener(new MyOnClickListener());
spinnerGrade.setOnItemSelectedListener(new MyOnItemSelectedListener());
}
//定義按鈕點擊監聽器
class MyOnClickListener implements View.OnClickListener {
//按鈕點擊
@Override
public void onClick(View view) {
if (view.getId() == R.id.buttonOk) {//被點擊的是確認按鈕
//獲取選中項
Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
//顯示提示框
Toast.makeText(MainActivity.this, gradeArray[spinnerGrade.getSelectedItemPosition()] , Toast.LENGTH_SHORT).show();
}
}
}
class MyOnItemSelectedListener implements AdapterView.OnItemSelectedListener {
//選擇
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
Toast.makeText(MainActivity.this, gradeArray[i], Toast.LENGTH_SHORT).show();
}
//未選擇
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
}
}