我正在编写一个应用程序，我需要通过点击它来放置用户必须加载图像的图像视图。点击后，我将为用户提供选项，让他们选择是否打算从手机本身加载存储的图像，或从相机拍摄新镜头。
这个问题可能是多余的，但几乎没有一个类似的问题/问题在这里没有达到我想要做的。
P.S。我正在使用安装了Eclipse 4.2（JUNO）SDK的Android API15。
以下是主要活动的代码段代码，它给出了一个错误：
package test.imgbyte.conerter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import android.net.Uri;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.widget.Button;
import android.widget.ImageView;
import android.view.View;
public class FindImgPathActivity extends Activity
{
private Uri mImageCaptureUri;
static final int CAMERA_PIC_REQUEST = 1337;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.imgfilepath);
Button camera = (Button) findViewById(R.id.btnLoad);
camera.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
cameraIntent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, mImageCaptureUri);
startActivityForResult(cameraIntent, CAMERA_PIC_REQUEST);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == CAMERA_PIC_REQUEST)
{
Bitmap thumbnail = (Bitmap) data.getExtras().get("data");
ImageView image = (ImageView) findViewById(R.id.imgLoaded);
image.setImageBitmap(thumbnail);
String pathToImage = mImageCaptureUri.getPath();
// pathToImage is a path you need.
// If image file is not in there,
// you can save it yourself manually with this code:
File file = new File(pathToImage);
FileOutputStream fOut;
try
{
fOut = new FileOutputStream(file);
thumbnail.compress(Bitmap.CompressFormat.JPEG, 100, fOut); // You can choose any format you want
}
catch (FileNotFoundException e)
{
e.printStackTrace();
}
}
}
}
我得到的错误是来自LogCat：
11-05 19:23:11.777: E/AndroidRuntime(1206): FATAL EXCEPTION: main
11-05 19:23:11.777: E/AndroidRuntime(1206): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1337, result=-1, data=Intent { act=inline-data (has extras) }} to activity {test.imgbyte.conerter/test.imgbyte.conerter.FindImgPathActivity}: java.lang.NullPointerException
答案 0 :(得分：4)
阿。这个错误。我花了很多时间来破译它的意思，显然结果有一些你想要访问的空字段。在你的情况下，你没有真正用文件初始化的mImageCaptureUri字段。启动相机意图的方法是创建一个文件，并将它的Uri作为EXTRA_OUTPUT传递给intent。
File tempFile = new File("blah.jpg");
...
cameraIntent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, Uri.fromFile(tempFile));
...
然后，您可以使用file.getAbsolutePath（）方法加载位图。
鉴于我们正处于这一点，让我与大家分享一下我上周学到的关于直接加载Bitmaps的非常重要的一点......不要这样做！我花了一个星期的时间来理解为什么，当我这么做的时候，我简直不敢相信我之前没有理解，这一切都是在记忆中发挥作用。
使用此代码有效加载位图。 （一旦你有了这个文件，只需在BitmapFactory.decodeFile（）中使用file.getAbsolutePath（））：
public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
if (width > height) {
inSampleSize = Math.round((float)height / (float)reqHeight);
} else {
inSampleSize = Math.round((float)width / (float)reqWidth);
}
}
return inSampleSize;
}
public static Bitmap decodeSampledBitmapFromPath(String path, int reqWidth, int reqHeight) {
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(path, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeFile(path, options);
}
只需将file.getAbsolutePath（）作为第一个参数传递，并将所需的宽度和高度传递给decodeSampledBitmapFromPath函数，以获得有效加载的位图。此代码已在Android文档的version here上进行了修改。
修改
private Uri mImageCaptureUri; // This needs to be initialized.
static final int CAMERA_PIC_REQUEST = 1337;
private String filePath;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.imgfilepath);
// Just a temporary solution, you're supposed to load whichever directory you need here
File mediaFile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "Temp1.jpg");
filePath = mediaFile.getABsolutePath();
Button camera = (Button) findViewById(R.id.btnLoad);
camera.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
cameraIntent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, Uri.fromFile(mediaFile));
startActivityForResult(cameraIntent, CAMERA_PIC_REQUEST);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == CAMERA_PIC_REQUEST)
{
if(resultCode == RESULT_OK)
{
int THUMBNAIL_SIZE = 64;
// Rest assured, if the result is OK, you're file is at that location
Bitmap thumbnail = decodeSampledBitmapFromPath(filePath, THUMBNAIL_SIZE, THUMBNAIL_SIZE); // This assumes you've included the method I mentioned above for optimization
ImageView image = (ImageView) findViewById(R.id.imgLoaded);
image.setImageBitmap(thumbnail);
}
}
}