Question

我希望能够记录应用程序所在的屏幕大小，以便我更容易获得适合不同Android屏幕尺寸的布局。我使用以下代码实现了一个名为layoutSizeAcitivty的类：

    public class LayoutSizeActivity extends SherlockActivity{

public void LayoutSize(){
    //Determine screen size
    if ((getResources().getConfiguration().screenLayout &Configuration.SCREENLAYOUT_SIZE_MASK) == Configuration.SCREENLAYOUT_SIZE_LARGE) 
    {     
        Log.d("Screen Size: ", "LARGE");
    }
    else if ((getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == Configuration.SCREENLAYOUT_SIZE_NORMAL) {     
        Log.d("Screen Size: ", "NORMAL");
    } 
    else if ((getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == Configuration.SCREENLAYOUT_SIZE_SMALL) {     
        Log.d("Screen Size: ", "SMALL");
    }
    else if ((getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == Configuration.SCREENLAYOUT_SIZE_XLARGE) {     
        Log.d("Screen Size: ", "XLARGE");
    }
    else {
        Log.d("Screen Size: ","UNKNOWN_CATEGORY_SCREEN_SIZE");
    }

    //Determine density
    DisplayMetrics metrics = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(metrics);
    int density = metrics.densityDpi;

    if (density==DisplayMetrics.DENSITY_HIGH) {
        Log.d("Screen Density: ","HIGH");
    }
    else if (density==DisplayMetrics.DENSITY_MEDIUM) {
        Log.d("Screen Density: ","MEDIUM");
    }
    else if (density==DisplayMetrics.DENSITY_LOW) {
        Log.d("Screen Density: ","LOW");
    }
    else if (density==DisplayMetrics.DENSITY_XHIGH) {
        Log.d("Screen Density: ","XHIGH");
    }
    else if (density==DisplayMetrics.DENSITY_XXHIGH) {
        Log.d("Screen Density: ","XXHIGH");
    }
    else {
        Log.d("Screen Density: ","UNKNOWN_CATEGORY");
    }
}

}

然后在onCreate方法的第一个活动中，我添加了这个：

private LayoutSizeActivity layoutSize;
layoutSize = new LayoutSizeActivity();
layoutSize.LayoutSize();

由于某种原因，我的LayoutSizeActivity.LayoutSize（）返回空指针异常。任何人都有任何想法，为什么会这样？感谢

Answer 1

private LayoutSizeActivity layoutSize;
layoutSize = new LayoutSizeActivity();

您无法使用Activity创建new的实例。不要尝试，它永远不会工作。

您可以使用Activity或其中一种类似方法（例如startActivity(...)等）创建startActivityForResult(...)的唯一方法。

Activity class

Activities Guide

Application Fundamentals

Android如何以编程方式确定我的应用程序使用的XML布局？

1 个答案: