java - 如何避免在android中方向改变时生成随机数

Question

我是 Android 新手，正在使用随机数开发示例应用程序。我在 Activity 中生成随机数，该随机数应用于相应布局中的某些 TextView 。每当我将方向从纵向更改为横向或从横向更改为纵向时，每次我旋转屏幕进行同一 Activity 时都会生成随机数值。因此，以前的值会丢失并生成新的数字。我尝试了很多方法，例如 android:configChanges="keyboardHidden|orientation" 以及保存和恢复我的一些值，但这些都没有给我一个正确的解决方案。对此有合适的解决方案吗？提前致谢。

Answer 1

当您更改方向时，您的 Activity 将被完全销毁并重新创建。所以每次它在定向后都会创建新的随机数。有一个重写方法 protected void onSaveInstanceState (Bundle outState)，您可以在其中将值存储在 bundle 对象中并在创建时检索它。

喜欢:

@Override
public void onSaveInstanceState(Bundle outState) {
    int value = 0; // test value
    outState.putInt("key",value);
    super.onSaveInstanceState(outState);
}
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if (savedInstanceState != null) {
        int randomInt = savedInstanceState.getInt("key");
    }
    // generate random number
}

更新:

private TextView first;
private TextView second;
private EditText editText;
private Button button;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initializeViews();
    if (savedInstanceState == null) {
        first.setText(getRandom());
        second.setText(getRandom());
    }
    else {
        first.setText(savedInstanceState.getString("first"));
        second.setText(savedInstanceState.getString("second"));
    }
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            int firstValue = Integer.parseInt(first.getText().toString());
            int secondValue = Integer.parseInt(second.getText().toString());
                int result = Integer.parseInt(editText.getText().toString());
                if( firstValue + secondValue == result )
                {
                    Toast.makeText(MainActivity.this, "Matched", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(MainActivity.this, "Wrong, try again", Toast.LENGTH_SHORT).show();
                }
            }
    });
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    outState.putString("first",first.getText().toString());
    outState.putString("second",second.getText().toString());
    super.onSaveInstanceState(outState);
}

private String getRandom() {
    return  Integer.toString((int)(Math.random()*10));
}

private void initializeViews() {
    first = (TextView)findViewById(R.id.first);
    second = (TextView)findViewById(R.id.second);
    editText = (EditText)findViewById(R.id.editText);
    button = (Button)findViewById(R.id.button);
}