非常基本的变量超出范围问题-Java Android

Question

我正在尝试使用以下3个变量：

public boolean mDetailsExpanded;

public int mHeightBefore;

public String mHeaderItem;

但是，当我将它们分配给字符串，布尔值和整数时：

 public void setMessageDetailsExpanded(MessageHeaderItem i, boolean expanded,
            int heightBefore) {
        mDiff = (expanded ? 1 : -1) * Math.abs(i.getHeight() - heightBefore);
        String mHeaderItem = i.toString();
        boolean  mDetailsExpanded = expanded;
        int mHeightBefore = heightBefore;             

    }

然后尝试稍后保存它们：

  @Override
    public void onSaveInstanceState(Bundle outState) {
        outState.putFloat(BUNDLE_KEY_WEBVIEW_Y_PERCENT, calculateScrollYPercent());
        outState.putBoolean(getTag(), mDetailsExpanded);
        outState.putInt(getTag(),  mHeightBefore);
        outState.putString(getTag(), mHeaderItem);
        super.onSaveInstanceState(outState);

    }

由于超出范围，它们不断返回null。 我如何纠正这个问题，使它们处于onSaveInstanceState的范围内，从而保持其值？

Answer 1

在setMessageDetailsExpanded ，您正在创建局部变量，而不是分配给成员变量。 更改为：

public void setMessageDetailsExpanded(MessageHeaderItem i, boolean expanded,
            int heightBefore) {
        mDiff = (expanded ? 1 : -1) * Math.abs(i.getHeight() - heightBefore);
        mHeaderItem = i.toString();
        mDetailsExpanded = expanded;
        mHeightBefore = heightBefore;             

}

Answer 2

String mHeaderItem = i.toString();
boolean  mDetailsExpanded = expanded;
int mHeightBefore = heightBefore;             

这是局部变量，其范围是方法范围。 这就是为什么在方法之外无法访问的原因。