ImageView 加载问题：在模拟器中有效，在真实设备中无效

Question

我在我的活动中显示了一个简单的ImageView：

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.package.name.EditPicture">

    <ImageView
        android:id="@+id/problem_picture"
        android:layout_width="wrap_content"
        android:layout_height="match_parent" />

</RelativeLayout>

在我的活动课程中，这是我设置图像的方式：

//first calculate the width and height of the screen
DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
int height = displaymetrics.heightPixels;
int width = displaymetrics.widthPixels;

//Then, resize the image's width and height equal to that of the screen:
Picasso.with(this).load(new File(pictureLocation)).rotate(90f).resize(height,width).into(imageView);

问题是，我在模拟器中得到了想要的结果，但在我真正的安卓手机中，什么都没有显示。整个屏幕都是空白的。

由于我已经将图像大小调整为屏幕大小，因此加载高分辨率图像应该没有任何问题。为什么在真机上我的屏幕是空白的？

Answer 1

首先检查设备上可用的图像。

File file = new File(pictureLocation);
if (file.exists()) {
    Picasso.with(this).load(new File(pictureLocation)).into(imageView);
} else {
    Log.d("Result", "Image not available");
}

Answer 2

我建议您在这种情况下使用 Content Provider。 我遇到了同样的问题，视图中加载的图像是黑色的。存储访问框架是这里的解决方案

https://developer.android.com/guide/topics/providers/document-provider.html

Answer 3

经过一番研究，这是原因和解决方案：

由于ImageView 无法加载大尺寸图像（相机为 13MP，图像为 3-4 MB），因此在真实设备中屏幕会变为空白。我尝试了一个较小的图像（~100 KB），效果很好。可惜毕加索和格莱德都做不到。

因此，我首先调整了图像的大小，然后将它们压缩到 100 KB 范围内（如果您想要全高清图像，则需要另一种方法）：

/**
 * getting the screen height and width, so that we could resize the image accordingly
 */
DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
int height = displaymetrics.heightPixels;
int width = displaymetrics.widthPixels;


/**
 * Getting the old photo and then resizing it to the size of the screen.
 * We are also compressing it. 70 is a number between 0 to 100.
 * You see, close to 0 means very low quality but very small in size image
 * Close to 100 means very high quality, but the size will be big.
 */
 Bitmap photo = BitmapFactory.decodeFile(pictureLocation);
 photo = Bitmap.createScaledBitmap(photo, width, height, false);
 ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 photo.compress(Bitmap.CompressFormat.JPEG, 70, bytes);


 /**
  * fetching the location where this has to be saved. folder location is the location of my Pictures folder.
  */
  String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
  String smallFileLocation = folderLocation + File.separator + "IMG_" + timeStamp + ".jpg";

  /**
   * New file is saved at this place now.
   */
  File f = new File(smallFileLocation);
  f.createNewFile();
  FileOutputStream fo = new FileOutputStream(f);
  fo.write(bytes.toByteArray());
  fo.close();


  /**
   * Later, we can simply put the picture in our ImageView using Picasso or just imageView.setImageBitmap
   */
  Picasso.with(this).load(new File(smallFileLocation)).rotate(90f).resize(height,width).into(imageView);

Answer 4

因为您加载的图片尺寸很大（例如：4000 像素 x 3000 像素）。 使用毕加索：

int width = new DeviceSize(mContext).widthPixels();
Picasso.get().load(fileUploadPath)
                                    .resize(width, 0)
                                    .onlyScaleDown()
                                    .into(imageView);

--类DeviceSize--

import android.content.Context;
import android.util.DisplayMetrics;

public class DeviceSize {

    private Context mContext;

    private int widthPixels;
    private int heightPixels;

    public DeviceSize(Context context) {
        mContext = context;
    }

    public int widthPixels() {
        DisplayMetrics lDisplayMetrics = mContext.getResources().getDisplayMetrics();
        widthPixels = lDisplayMetrics.widthPixels;
        return widthPixels;
    }

    public int heightPixels() {
        DisplayMetrics lDisplayMetrics = mContext.getResources().getDisplayMetrics();
        heightPixels = lDisplayMetrics.heightPixels;
        return heightPixels;
    }
}