简易计程器

Question

我想做一个简单的计算器。客户将输入 he/she 行驶了多少公里，计算器将给出总金额。开通数量为4，每公里费率为1.4。

我做错了什么？

public class MainActivity extends AppCompatActivity {

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

        double km;
        int y;
        double x;
        x = 1.4;
        y = 4;

        TextView tabela = (TextView) findViewById(R.id.tabela);
        EditText number = (EditText) findViewById(R.id.number);
        String written = number.getText().toString();
        km = Double.parseDouble(written);
        tabela.setText("Total Amount" + ((km*x)+y));
    }
}

Answer 1

number.getText().toString()立即returns一个空字符串。

您需要一个 Button 和一个点击侦听器。

public class MainActivity extends AppCompatActivity 
    implements View.OnClickListener {

    TextView tabela;
    EditText number;
    Button b;

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.button) {
            String written = number.getText().toString();
            km = Double.parseDouble(written);
            tabela.setText("Total Amount" + ((km*x)+y));
        }
    }

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

        tabela = (TextView) findViewById(R.id.tabela);
        number = (EditText) findViewById(R.id.number);

        b = ... // find button here
        b.setOnClickListener(this); // to the activity

简易计程器

Simple TaxiMeter

java

android

calculator