根据在另一个微调器中选择的微调器中的项目显示数据？

Question

我已经为 select 一个状态编写了一个程序，根据 selected 状态，它显示了其中的城市，但没有显示城市，请帮助

这是 MainActivity

public class MainActivity extends AppCompatActivity {
Spinner state, city;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    state= (Spinner) findViewById(R.id.spinner);
    city= (Spinner) findViewById(R.id.spinner2);
    ArrayAdapter<CharSequence> adapter= ArrayAdapter.createFromResource(this,R.array.states,android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    state.setAdapter(adapter);
    state.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            String state= parent.getItemAtPosition(position).toString();
            Toast.makeText(MainActivity.this, "State = "+state, Toast.LENGTH_SHORT).show();
            city= (Spinner) findViewById(R.id.spinner2);
            if (state=="Rajasthan"){
                ArrayAdapter<CharSequence> adapter1= ArrayAdapter.createFromResource(getApplicationContext(),R.array.cities_rajasthan,android.R.layout.simple_spinner_item);
                adapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                city.setAdapter(adapter1);

            }
            else if (state=="Madhya Pradesh"){
                ArrayAdapter<CharSequence> adapter2= ArrayAdapter.createFromResource(getApplicationContext(),R.array.cities_madhyapradesh,android.R.layout.simple_spinner_item);
                adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                city.setAdapter(adapter2);
            }
            else if (state=="Uttar Pradesh"){
                ArrayAdapter<CharSequence> adapter3= ArrayAdapter.createFromResource(getApplicationContext(),R.array.cities_uttarpradesh,android.R.layout.simple_spinner_item);
                adapter3.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                city.setAdapter(adapter3);
            }
            else if (state=="Maharashtra"){
                ArrayAdapter<CharSequence> adapter4= ArrayAdapter.createFromResource(getApplicationContext(),R.array.cities_maharashtra,android.R.layout.simple_spinner_item);
                adapter4.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                city.setAdapter(adapter4);
            }

        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {
            Toast.makeText(MainActivity.this, "Nothing is Selected ", Toast.LENGTH_SHORT).show();
        }
    });
}}

这是 String.xml 文件

<resources>
<string name="app_name">Spinners2</string>
<string-array name="states">
    <item>Rajasthan</item>
    <item>Madhya Pradesh</item>
    <item>Maharashtra</item>
    <item>Uttar Pradesh</item>
</string-array>
<string-array name="cities_rajasthan">
    <item>Bikaner</item>
    <item>Jaipur</item>
    <item>Jodhpur</item>
    <item>Jaisalmer</item>
</string-array>
<string-array name="cities_madhyapradesh">
    <item>Indore</item>
    <item>Bhopal</item>
    <item>Jabalpur</item>
    <item>Ujjain</item>
</string-array>
<string-array name="cities_maharashtra">
    <item>Pune</item>
    <item>Mumbai</item>
    <item>Nagpur</item>
</string-array>
<string-array name="cities_uttarpradesh">
    <item>Lucknow</item>
    <item>Agra</item>
    <item>Kanpur</item>
</string-array>
</resources>

这是activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.saranshagarwal.spinners2.MainActivity">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="State"
    android:id="@+id/textView"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_marginTop="60dp" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="City"
    android:id="@+id/textView2"
    android:layout_below="@+id/spinner"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />

<Spinner
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/spinner"
    android:layout_below="@+id/textView"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />

<Spinner
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/spinner2"
     android:layout_below="@+id/textView2"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />
</RelativeLayout>

Answer 1

这样试试，

state.setOnItemSelectedListener(
  new OnItemSelectedListener() {
      public void onItemSelected(
            AdapterView<?> parent, View view, int position, long id) {
                String selected_item = state.getSelectedItem().toString();

                if(selected_item.equals("Rajastan"))
                {
                    //do your operation here
                }
                elseif(..)
                {
                ..
                }
                //etc

        }

            public void onNothingSelected(AdapterView<?> parent) {
                 Toast.makeText(MainActivity.this, "Nothing is Selected ", Toast.LENGTH_SHORT).show();
            }
});

使用String.equals()

这可能对你有帮助。

编码愉快!!!!

Answer 2

您的代码的问题是您正在比较两个带有 == 符号的字符串，而它们是不同的对象。

而不是 == 使用 String.equals(object)

改变这个：

if (state=="Rajasthan")

收件人：

if(state.equals("Rajasthan")){
 //Set adapter
}

如果你使用 switch 个案例而不是 if-else 个语句，它会更好更容易。

根据在另一个微调器中选择的微调器中的项目显示数据？

Displaying data according to the item in the spinner selected in another spinner?

android

spinner