我正在关注此Android开发人员的教程:http://developer.android.com/training/camera/photobasics.html
我使用了本教程中的确切代码。但是,它在createImageFile()
函数中创建图像文件时返回null。
请你看看我的代码并告诉我我错过了什么?
public class MainActivity extends AppCompatActivity {
private static final int REQUEST_IMAGE_CAPTURE = 1;
ImageView mImageView;
String mCurrentPhotoPath;
Button takepicturebtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mImageView = (ImageView) findViewById(R.id.imageView);
takepicturebtn = (Button) findViewById(R.id.takepicturebtn);
takepicturebtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
dispatchTakePictureIntent();
}
});
}
private File createImageFile() throws IOException {
// Create an image file name
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
String imageFileName = "JPEG_" + timeStamp + "_";
File storageDir = Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_PICTURES);
File image = File.createTempFile(
imageFileName, /* prefix */
".jpg", /* suffix */
storageDir /* directory */
);
// Save a file: path for use with ACTION_VIEW intents
mCurrentPhotoPath ="file:" + image.getAbsolutePath();
return image;
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
setPic();
}
}
private void dispatchTakePictureIntent() {
Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
// Ensure that there's a camera activity to handle the intent
if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
// Create the File where the photo should go
File photoFile = null;
try {
photoFile = createImageFile();
} catch (IOException ex) {
// Error occurred while creating the File
}
// Continue only if the File was successfully created
if (photoFile != null) {
takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT,
Uri.fromFile(photoFile));
startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
}
}
}
private void setPic() {
// Get the dimensions of the View
int targetW = mImageView.getWidth();
int targetH = mImageView.getHeight();
// Get the dimensions of the bitmap
BitmapFactory.Options bmOptions = new BitmapFactory.Options();
bmOptions.inJustDecodeBounds = true;
BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions);
int photoW = bmOptions.outWidth;
int photoH = bmOptions.outHeight;
// Determine how much to scale down the image
int scaleFactor = Math.min(photoW/targetW, photoH/targetH);
// Decode the image file into a Bitmap sized to fill the View
bmOptions.inJustDecodeBounds = false;
bmOptions.inSampleSize = scaleFactor;
bmOptions.inPurgeable = true;
Bitmap bitmap = BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions);
mImageView.setImageBitmap(bitmap);
}
}
这是我的清单文件:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.figengungor.takingcamerapicture" >
<uses-feature android:name="android.hardware.camera"></uses-feature>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="18" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme" >
<activity android:name=".MainActivity" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
答案 0 :(得分:2)
我是这个网站上的新手,但我已经遇到了同样的问题。我做了什么: 在Manifest中我使用了这样的代码:
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-feature android:name="android.hardware.camera"></uses-feature>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
...
<activity android:name=".MainActivity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:screenOrientation="portrait">
由于我没有为我的应用程序使用横向方向,因此每次按下按钮时都会从相机中保存图片,新的MainActivity正在创建,而OnCreated方法再次调用。但是创建了前一个文件。 至于Inten数据 - 它仍然是null,所以我把ImageView放在我的文件中(之前更改大小)。我没有使用方法setPic(),而是使用这段代码(不要忘记在课堂上初始化File photoFile):
bitmap = BitmapFactory.decodeFile(photoFile.getAbsolutePath());
imageView = (ImageView) findViewById(R.id.imageView);
// Resize the bitmap to 150x100 (width x height)
Bitmap bMapScaled = Bitmap.createScaledBitmap(bitmap, 150, 100, true);
// Loads the resized Bitmap into an ImageView
imageView.setImageBitmap(bMapScaled);
或 您可以使用方法setPic(),但需要在此方法mCurrentPhotoPath中的任何位置更改为photoFile.getAbsolutePath()。它有效。
希望它有所帮助。
答案 1 :(得分:0)
我使用了本教程中的确切代码
实际上,你把你应该选择的东西组合在一起。
The Save the Full-Size Photo section让你 使用Environment.getExternalStoragePublicDirectory()
或使用getExternalFilesDir()
。你选择了前者,这很好。但是,您还将android:maxSdkVersion
添加到<uses-permission>
元素,这是使用getExternalFilesDir()
的说明的一部分。您需要在所有相关Android版本上使用WRITE_EXTERNAL_STORAGE
才能使用Environment.getExternalStoragePublicDirectory()
。
您有三种选择:
删除android:maxSdkVersion
。然后,请确保targetSdkVersion
(在app/build.gradle
中,假设您有传统的Android Studio项目)为22或更低,或者您在Android 5.1或更低版本上进行测试。
删除android:maxSdkVersion
,同时将targetSdkVersion
保留为23(或更高),并在Android 6.0(或更高版本)上进行测试。在这种情况下,您还必须处理WRITE_EXTERNAL_STORAGE
在Android 6.0+上具有dangerous
权限这一事实,并且需要通过运行时权限系统进行处理。
切换为使用getExternalFilesDir()
代替Environment.getExternalStoragePublicDirectory()
。