如何在对话框或浮动活动中创建计算器？

Question

我想创建一个以这种方式运作的“计算器”：当我在MainActivity时，按下TextView，Dialog（或Theme.DeviceDefault.Light.Dialog的活动}主题或类似的东西）用键盘打开，我可以在其中进行操作，结果将更改TextView的文本。结果将是这样的：

Image - MainActivity.class

Image - IncreaseReduce.class

问题是每次按“+”或“ - ”并且应用程序关闭IncreaseReduce活动时，MainActivity会重新初始化并{{1方法是调用（我推测）。例如，如果我想添加5，则应用程序将5添加到默认值（在本例中为1000）。每次都会发生这种情况，因此我不能执行以下操作：previous_result + 5 + 10（结果1015）。结果将是1010.我该如何解决？此外，我更喜欢使用对话，但我不喜欢如何 这是我的代码：

MainActivity.class

onCreate

EncreaseReduce.class

public class MainActivity extends AppCompatActivity {
private TextView textView;
private String toEncreaseReduce = "";
private int operation = -1;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    textView = (TextView) findViewById(R.id.textView);
    textView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(MainActivity.this, IncreaseReduce.class);
            startActivity(intent);
        }
    });
    Bundle b = getIntent().getExtras();
    if(b != null) {
        toEncreaseReduce = b.getString("to");
        operation = b.getInt("operation");
    }
    if(operation != -1 && toEncreaseReduce != "")
        operate(toEncreaseReduce,operation);
}

public void operate(String toEncreaseReduce, int operation)
{

    long lpInt;
    String lpString;;
    long op;
        lpString = textView.getText().toString();
        lpInt = Long.parseLong(lpString);
        op = Long.parseLong(toEncreaseReduce);
        if (operation == 1)
            lpInt = lpInt + op;
        if(operation == 2)
            lpInt = lpInt - op;
        textView.setText("" + Long.toString(lpInt));
}
}

清单

public class IncreaseReduce extends Activity implements View.OnClickListener{


private Button button1;
private Button button2;
private Button button3;
private Button button4;
private Button button5;
private Button button6;
private Button button7;
private Button button8;
private Button button9;
private Button buttonm;
private Button button0;
private Button buttonp;
private String lp;
private String number = "";
@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.increase_reduce_layout);

    button0 = (Button) findViewById(R.id.b0);
    button1 = (Button) findViewById(R.id.b1);
    button2 = (Button) findViewById(R.id.b2);
    button3 = (Button) findViewById(R.id.b3);
    button4 = (Button) findViewById(R.id.b4);
    button5 = (Button) findViewById(R.id.b5);
    button6 = (Button) findViewById(R.id.b6);
    button7 = (Button) findViewById(R.id.b7);
    button8 = (Button) findViewById(R.id.b8);
    button9 = (Button) findViewById(R.id.b9);
    buttonp = (Button) findViewById(R.id.bp);
    buttonm = (Button) findViewById(R.id.bm);

    button0.setOnClickListener(this);
    button1.setOnClickListener(this);
    button2.setOnClickListener(this);
    button3.setOnClickListener(this);
    button4.setOnClickListener(this);
    button5.setOnClickListener(this);
    button6.setOnClickListener(this);
    button7.setOnClickListener(this);
    button8.setOnClickListener(this);
    button9.setOnClickListener(this);
    buttonp.setOnClickListener(this);
    buttonm.setOnClickListener(this);

}

@Override
public void onClick(View v)
{
    switch(v.getId())
    {
        case(R.id.b0):
            number = number + "0";
            setTitle(number);
            break;
        case(R.id.b1):
            number = number + "1";
            setTitle(number);
            break;
        case(R.id.b2):
            number = number + "2";
            setTitle(number);
            break;
        case(R.id.b3):
            number = number + "3";
            setTitle(number);
            break;
        case(R.id.b4):
            number = number + "4";
            setTitle(number);
            break;
        case(R.id.b5):
            number = number + "5";
            setTitle(number);
            break;
        case(R.id.b6):
            number = number + "6";
            setTitle(number);
            break;
        case(R.id.b7):
            number = number + "7";
            setTitle(number);
            break;
        case(R.id.b8):
            number = number + "8";
            setTitle(number);
            break;
        case(R.id.b9):
            number = number + "9";
            setTitle(number);
            break;
        case(R.id.bp):
            passage(1, number);
            break;
        case(R.id.bm):
            passage(2, number);
            break;

    }
}
public void passage(int operation, String toIncreaseReduce)
{
    /*
    * 1: add
    * 2: reduce
     */
    Intent intent = new Intent(IncreaseReduce.this,  MainActivity.class);
//        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
        if (toIncreaseReduce != "") {
            Bundle b = new Bundle();
            b.putString("to", number);
            b.putInt("operation",1);
            intent.putExtras(b); //Put your id to your next Intent
        }
        startActivity(intent);
        finish();
   }


}

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