Question

我正在尝试创建一个计算器应用程序，显示用户在编辑文本屏幕上单击的所有内容，但是，当用户单击按钮时，编辑文本屏幕仍然为空白。我已经写了一些印刷语句来看看会发生什么，这就是我发现的：

updateEditText()中的print语句始终为空，即使用户单击按钮，但getValuesPressed()中的print语句也会成功打印出单击按钮的位置。

我不明白我做错了什么。

这就是我所拥有的：

    void updateEditText(){
    EditText et = (EditText) findViewById(R.id.editText);
    System.out.println("THE VALUE PRESSED IS: " + getValuesPressed());
    et.setText(getValuesPressed());//problem here
}

//return and concat the buttons that were clicked
String getValuesPressed(){

    for(int i = 0; i < buttonList.length; i++){

        final int j = i;
        buttonList[i].setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                System.out.println("THE BUTTON WAS PRESSED: " + buttonList[j].getText());
                switch(j){

                    case 0://CLEAR
                        textOnScreen = "0";
                        break;

                    case 5://SQRT
                        solveEquation();
                        //CASE: IF IT IS NEG U CANT TAKE THE SQRT!!!!
                        textOnScreen = String.valueOf(Math.sqrt(Double.parseDouble(textOnScreen)));
                        break;

                    case 18: //NEGATIVE
                        if(textOnScreen.charAt(textOnScreen.length() - 1) != '-')
                            textOnScreen = textOnScreen + "-";
                        else
                            textOnScreen = textOnScreen.substring(0, textOnScreen.length() - 1);
                        break;

                    case 19: //BACKSPACE
                        if(textOnScreen.length() == 1)
                            textOnScreen = "0";
                        else
                            textOnScreen = textOnScreen.substring(0, textOnScreen.length() - 1);
                        break;

                    case 20: //SOLVE
                        solveEquation();
                        break;

                    default://concat all of the other buttons pressed
                        textOnScreen = textOnScreen + buttonList[j].getText();
                        break;
                }
            }
        });
    }
    return textOnScreen;
}

Answer 1

您不应该为每个按钮多次设置OnClickListener。将String getValuesPressed（）函数更改为void setButtonClickEvents（）。

此外，您不需要updateEditText（）函数。而不是连接textOnScreen，直接连接EditText：

case 0://CLEAR
    et.setText("0");
    break;

case 5://SQRT
    solveEquation();
    //CASE: IF IT IS NEG U CANT TAKE THE SQRT!!!!
    et.setText(String.valueOf(Math.sqrt(Double.parseDouble(et.getText().toString())));
    break;

等等。

Answer 2

您的整个代码对我来说并不合理。您应该做的第一件事是为所有按钮添加onClickListener。这个监听器看起来像这样：

@Override
        public void onClick(View v) {

            System.out.println("THE BUTTON WAS PRESSED: " + ((Button)v).getText();
            switch(v.getId()){

                case R.id.<ID of this Button>://CLEAR
                    et.setText("0");
                    break;

                case R.id.<ID of this Button>://SQRT
                    solveEquation();
                    //CASE: IF IT IS NEG U CANT TAKE THE SQRT!!!!
                    et.setText(String.valueOf(Math.sqrt(Double.parseDouble(textOnScreen))));
                    break;

                case R.id.<ID of this Button>: //NEGATIVE
                    if(et.getText().charAt(et.getText().length() - 1) != '-')
                        et.setText(et.getText + "-");
                    else
                        et.setText(et.getText().toString().substring(0, et.getText().length() - 1));
                    break;

                case R.id.<ID of this Button>: //BACKSPACE
                    if(et.getText().length() == 1)
                        et.setText("0");
                    else
                        et.setText(et.getText().toString()substring(0, et.getText().length() - 1));
                    break;

                case R.id.<ID of this Button>: //SOLVE
                    solveEquation();
                    break;
            }
        }

当用户按下按钮时如何在编辑文本上显示值？

2 个答案: