android - TextView 由于某种原因无法清除，Android

Question

我希望这不是一个愚蠢的问题。我在清除 TextView 时遇到了一些问题。我环顾四周，每个人都在说使用:textView.setText("");在 onCreate 但由于某种原因似乎不起作用。基本上，我的应用程序只接受来自 editText 的数字，然后运行 ​​Fibonacci 数列(当单击按钮时)并在 textView 中显示结果。好吧，序列显示正常，但我希望每次单击按钮时清除 TextView - 到目前为止，它只是不断向已有内容添加更多文本。

我是在放置 textView.setText("");在错误的位置？还是我只是缺少其他一些概念？ (我也试过从我的 OnClick 中放置它——这也没有用)。

这是我的代码:

public class MainActivity extends Activity {

// primary widgets
private EditText editText;
private TextView textView;
private Button button1;

static ArrayList<Integer> fibList = new ArrayList<Integer>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    editText = (EditText) findViewById(R.id.editText1);
    textView = (TextView) findViewById(R.id.textView2);
    button1 = (Button) findViewById(R.id.button1);

    //Attempt to clear TextView
    textView.setText("");

    button1.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

            String input = editText.getText().toString();
            int number = Integer.parseInt(input);
            int tmp = 0;

            // confirm input
            if (number < 20) {
                Toast.makeText(getApplicationContext(),
                        "You entered: " + number, Toast.LENGTH_LONG).show();
                for (int i = 0; i <= number; i++) {
                    fibList.add(fib(i));

                    // sum even numbers
                    if (fib(i) % 2 == 0) {
                        tmp += fib(i);

                    }

                }
            } else {
                Toast.makeText(getApplicationContext(),
                        "Number is too Large: " + number, Toast.LENGTH_LONG)
                        .show();
            }
            String array = fibList.toString();
            textView.setText(array);

        }

    });

}

// run fibonacci sequence
public static int fib(int n) {
    if (n < 2) {
        return n;
    } else {
        return fib(n - 1) + fib(n - 2);
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

Answer 1

如果您希望在每次单击按钮时清除 TextView，则必须在 onClick 中加入 .setText。您将 .setText 放在 onCreate 中的原因是在您的 Activity 创建后立即清除文本，但由于您的按钮还没有被按下，所以 setText 什么都不做。此外，由于您的 onCreate 只会为您的 Activity 运行一次，因此它永远不会再次返回到 setText。尝试以下操作:

    public class MainActivity extends Activity {

// primary widgets
private EditText editText;
private TextView textView;
private Button button1;

static ArrayList<Integer> fibList = new ArrayList<Integer>();
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    editText = (EditText) findViewById(R.id.editText1);
    textView = (TextView) findViewById(R.id.textView2);
    button1 = (Button) findViewById(R.id.button1);



    button1.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            textView.setText(""); //Clear the TextView
            fibList.clear(); //Clear your array list before adding new elements

            String input = editText.getText().toString();
            int number = Integer.parseInt(input);
            int tmp = 0;

            // confirm input
            if (number < 20) {
                Toast.makeText(getApplicationContext(),
                        "You entered: " + number, Toast.LENGTH_LONG).show();
                for (int i = 0; i <= number; i++) {
                    fibList.add(fib(i));

                    // sum even numbers
                    if (fib(i) % 2 == 0) {
                        tmp += fib(i);

                    }

                }
            } else {
                Toast.makeText(getApplicationContext(),
                        "Number is too Large: " + number, Toast.LENGTH_LONG)
                        .show();
            }
            String array = fibList.toString();
            textView.setText(array);

        }

    });

}

// run fibonacci sequence
public static int fib(int n) {
    if (n < 2) {
        return n;
    } else {
        return fib(n - 1) + fib(n - 2);
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

}