如何使我的變量=下拉菜單中的項目

Question

我有一個具有16個值的微調框。 24，24 1/16，24 2/16 .... 25.我要選擇一個，然后將其放入double（decimal）形式的變量“ w”中。 我想在下面的計算中使用該變量。 為了簡單起見，我只編寫了三個if語句，但是只要知道它會以某種方式影響它，我就會知道其中有16個。 但是在計算中，它們顯示為未定義。

public void calculate(View view) {
    EditText length_find = findViewById(R.id.feet);
    EditText pounds_find = findViewById(R.id.pounds);
    DecimalFormat df = new DecimalFormat("###.###");


    Spinner width_select = findViewById(R.id.width_select);

    ArrayAdapter<String> myAdapter = new ArrayAdapter<>(MainActivity.this, android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.width));
    myAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    width_select.setAdapter(myAdapter);

    width_select.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Object item = parent.getItemAtPosition(position);
            if (position == 0){
                double w = 24;

            }
            if (position == 1){
                double w = 24.0625;
            }
            if (position == 2){
                double w = 24.125;
            }
        }
    });



    try {

        double d = .29;
        double h = .002;



        //This Calculates if Pounds are given
        if (length_find.getText().toString().equals("")){
            Toast.makeText(MainActivity.this, "Given Pounds", LENGTH_LONG).show();
            double pounds = Double.parseDouble(pounds_find.getText().toString());


            //THIS IS THE MATH PORTION

            double length_d = (pounds / (w * h * d * 12));


            String length = Double.toString(Double.parseDouble(df.format(length_d)));
            final TextView zTextView = (TextView) findViewById(R.id.length_show);
            zTextView.setText("Feet: " + length);
            final TextView mTextView = (TextView) findViewById(R.id.pound_show);
            mTextView.setText("Pounds: ");
            length_find.getText().clear();
            pounds_find.getText().clear();
        }


        //This Calculates if Length is given
        if (pounds_find.getText().toString().equals("")){
          Toast.makeText(MainActivity.this, "Given Length", LENGTH_LONG).show();
          Double length = Double.parseDouble(length_find.getText().toString());





          //THIS IS THE MATH PORTION


          double answer_pounds_d = (w * h * length * 12 * d);







            String answer_pounds = Double.toString(Double.parseDouble(df.format(answer_pounds_d)));
          final TextView mTextView = (TextView) findViewById(R.id.pound_show);
          mTextView.setText("Pounds: " + answer_pounds);
          final TextView zTextView = (TextView) findViewById(R.id.length_show);
          zTextView.setText("Feet: ");
          length_find.getText().clear();
          pounds_find.getText().clear();



        }
        if((pounds_find).getText().toString().trim().length() > 0 && (length_find).getText().toString().trim().length() > 0){
            Toast.makeText(MainActivity.this, "Whata hell you need me for mate!", LENGTH_LONG).show();
        }

    }
    catch(Exception ex) {
            //Toast.makeText(this, "Error", Toast.LENGTH_SHORT).show();
        }

    }

Answer 1

由於您僅在onItemClick的if語句中創建變量，因此只能在這些if語句中訪問它們。 我的建議可能是在if語句之前創建它，然后在語句中為其分配一個值。 為了使用它，您可能必須將所有數學和內容移到onItemClick內部。

編輯：未經測試，但我的猜測將是這樣的：

public void calculate(View view) {
    EditText length_find = findViewById(R.id.feet);
    EditText pounds_find = findViewById(R.id.pounds);
    DecimalFormat df = new DecimalFormat("###.###");


    Spinner width_select = findViewById(R.id.width_select);

    ArrayAdapter<String> myAdapter = new ArrayAdapter<>(MainActivity.this, android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.width));
    myAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    width_select.setAdapter(myAdapter);

    width_select.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Object item = parent.getItemAtPosition(position);
           double w = 0;


            if (position == 0){
                double w = 24;

            }
            if (position == 1){
                double w = 24.0625;
            }
            if (position == 2){
                double w = 24.125;
            }
    try {

        double d = .29;
        double h = .002;



        //This Calculates if Pounds are given
        if (length_find.getText().toString().equals("")){
            Toast.makeText(MainActivity.this, "Given Pounds", LENGTH_LONG).show();
            double pounds = Double.parseDouble(pounds_find.getText().toString());


            //THIS IS THE MATH PORTION

            double length_d = (pounds / (w * h * d * 12));


            String length = Double.toString(Double.parseDouble(df.format(length_d)));
            final TextView zTextView = (TextView) findViewById(R.id.length_show);
            zTextView.setText("Feet: " + length);
            final TextView mTextView = (TextView) findViewById(R.id.pound_show);
            mTextView.setText("Pounds: ");
            length_find.getText().clear();
            pounds_find.getText().clear();
        }


        //This Calculates if Length is given
        if (pounds_find.getText().toString().equals("")){
          Toast.makeText(MainActivity.this, "Given Length", LENGTH_LONG).show();
          Double length = Double.parseDouble(length_find.getText().toString());





          //THIS IS THE MATH PORTION


          double answer_pounds_d = (w * h * length * 12 * d);







            String answer_pounds = Double.toString(Double.parseDouble(df.format(answer_pounds_d)));
          final TextView mTextView = (TextView) findViewById(R.id.pound_show);
          mTextView.setText("Pounds: " + answer_pounds);
          final TextView zTextView = (TextView) findViewById(R.id.length_show);
          zTextView.setText("Feet: ");
          length_find.getText().clear();
          pounds_find.getText().clear();



        }
        if((pounds_find).getText().toString().trim().length() > 0 && (length_find).getText().toString().trim().length() > 0){
            Toast.makeText(MainActivity.this, "Whata hell you need me for mate!", LENGTH_LONG).show();
        }

    }
    catch(Exception ex) {
            //Toast.makeText(this, "Error", Toast.LENGTH_SHORT).show();
        }

    }
        }
    });

Answer 2

只需將變量“ w”設置為活動的全局變量即可。因為變量“ w”屬於'if語句'范圍的局部變量，並且在其外部未定義。