android - 从资源设置壁纸

Question

我有一个关于 wallpapermanager 的简单问题，我无法在此站点上找到答案。我有一个非常简单的代码和一张 1280x800 的图片(我的平板电脑的显示屏)。当我运行代码时，我只得到图像的中心作为墙纸，好像整个图片被放大了。这是为什么？谢谢!

package com.daniel.wallpaperPorsche;

import java.io.IOException;
import com.daniel.wallpaper.R;
import android.os.Bundle;
import android.app.Activity;
import android.app.WallpaperManager;
import android.view.Menu;
import android.widget.Toast;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);  

WallpaperManager myWallpaperManager = WallpaperManager.getInstance(this);

try {
     myWallpaperManager.setResource(R.drawable.porsche_911_1280x800_72dpi);

     Toast.makeText(getBaseContext(), "Success set as wallpaper", Toast.LENGTH_SHORT).show();

} catch (IOException e) {
     Toast.makeText(getBaseContext(), "Error set as wallpaper", Toast.LENGTH_SHORT).show();

  } 
  super.onDestroy();
  }  
}

Answer 1

我发现在没有任何缩放问题的情况下设置墙纸的最佳方法(这通常看起来完全是任意的，正如您在分辨率大小相同时看到的那样)是使用 BitmapFactory。您将使用 WallpaperManager.setBitmap 而不是 WallpaperManager.setResource。

String path = "path/to/desired/wallpaper/file";
final BitmapFactory.Options options = new BitmapFactory.Options();

//The inJustDecodeBounds option tells the decoder to return null (no bitmap), but it does 
//include the size of the image, letting us query for the size.

options.inJustDecodeBounds = true; 
BitmapFactory.decodeFile(path_, options);

// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, width, height);

// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
Bitmap decodedSampleBitmap = BitmapFactory.decodeFile(path_, options);

//wm = WallpaperManager
wm.suggestDesiredDimensions(decodedSampleBitmap.getWidth(), decodedSampleBitmap.getHeight());
wm.setBitmap(decodedSampleBitmap);

calculateInSampleSize是谷歌在android文档中实际提供实现的方法；他们的目标是有效地加载大型位图。您可以在这里阅读:http://developer.android.com/training/displaying-bitmaps/load-bitmap.html

不幸的是，他们的实现很糟糕，而且经常出错。我会推荐这个。

public static int calculateInSampleSize(
        BitmapFactory.Options options, int reqWidth, int reqHeight) {
    // Raw height and width of image
    int imageHeight = options.outHeight;
    int imageWidth = options.outWidth;
    int inSampleSize = 1;

    int multiplyHeight = 1;
    int multiplyWidth = 1;

    while (imageHeight >= reqHeight)
    {
        multiplyHeight++;
        imageHeight = imageHeight/2;
    }
    while (imageWidth >= reqWidth)
    {
        multiplyWidth++;
        imageWidth = imageWidth/2;
    }

    if (multiplyHeight > multiplyWidth)
        return multiplyHeight;
    else
        return multiplyWidth;

}

此方法对于加载大文件更有效，可以防止 OutOfMemoryException，并且还应该避免您看到的奇怪的缩放。如果没有，请告诉我，我会重新审视我所做的事情。