上代码：

spinner = (Spinner) findViewById(R.id.spinner);
        tv = (TextView) findViewById(R.id.tv);
        final ArrayList<String> list = new ArrayList<>();
        list.add("不知道");
        list.add("A");
        list.add("B");
        list.add("AB");
        list.add("O");

        //这里的R.Layout.spinner_item为spinner的样式
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this,R.layout.spinner_item);

        //这里的R.layout.spinner_item_item为下拉框textview的样式

        adapter.setDropDownViewResource(R.layout.spinner_item_item);
        adapter.addAll(list);
        spinner.setAdapter(adapter);

        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                tv.setText("你的血型："+list.get(i));

            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {

            }
        });
        spinner.setSelection(0);

    }

}

xml:R.layout.spinner_item:

<?xml version="1.0" encoding="utf-8"?>
<CheckedTextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:singleLine="true"
    android:background="#5888"
    android:gravity="center"
    android:layout_height="33dp">

</CheckedTextView>

xml:R.layout.spinner_item_item:

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:background="#3999"
    android:layout_marginTop="2dp"
    android:gravity="center"
     android:layout_width="match_parent"
    android:layout_height="33dp">

</TextView>

demo下载地址：https://github.com/renjiemei1225/SpinnerTest