Spinner中的条件项

我正在尝试在 Spinner 基于另一个中的选定值 旋转器 .

Spinner spin1 = (Spinner) findViewById(R.id.Spinner1);
spin1.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
    public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
        Object Obj = parent.getItemAtPosition(pos);
        String str = Obj.toString();
        Log.i(str, str);
        if (str == "B") {
            Spinner spin2 = (Spinner) findViewById(R.id.Spinner2);
            ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
                    getApplicationContext(), R.array.array1,
                    android.R.layout.simple_spinner_item);
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            spin2.setAdapter(adapter);
        } else if (str=="M") {
            Spinner spin2 = (Spinner) findViewById(R.id.Spinner2);
            ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
                    getApplicationContext(), R.array.array2,
                    android.R.layout.simple_spinner_item);
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            spin2.setAdapter(adapter);
        }
    }

我在经历了不同的论坛之后汇编了这段代码。但这对我不起作用 Log.i 正在为我提供所选的正确城市,但第二个微调器未填充新阵列。