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;

然而，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 return null。我怎样才能更正它以将它们置于 onSaveInstanceState 的范围内从而保持它们的值？

Answer 1

在 setMessageDetailsExpanded 中，您正在创建局部变量而不是分配给您的成员变量。将其更改为：

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，它的作用域是方法作用域。这就是为什么无法在方法之外访问的原因。

非常基本的变量超出范围问题 - Java Android

Very Basic Variable Out of Scope Issue - Java Android

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