如何从 Activity 调用一个类
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【中文标题】如何从 Activity 调用一个类【英文标题】：How to call a class from Activity 【发布时间】：2014-02-12 02:31:28 【问题描述】：我是 android 开发的新手，我正在开发一个程序来从相机捕获图像并存储在 SD 卡中。问题是我单独创建 Camera 类并尝试调用 capture_image Activity。这是我的代码。请帮我解决这个问题。
这就是我调用相机类的方式
Camera cam=new Camera();
fileUri= cam.captureImage();
这里是 capture_image 活动
package com.example.imagecapture;
import java.io.File;
import java.io.FileOutputStream;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.location.Location;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
import android.widget.Toast;
public class capture_image extends Activity
private Uri fileUri;
private static final int CAMERA_CAPTURE_IMAGE_REQUEST_CODE = 100;
private static int RESULT_LOAD_IMAGE = 1;
private ImageView image1;
private ImageView image2;
private ImageView image3;
private ImageView image4;
private ImageView image5;
private ImageView image6;
private ImageView image7;
private ImageView image8;
//private LocationManager locationManager;
private ImageView[] IMGS = image1, image2, image3,image4,image5,image6,image7,image8 ;
private File file;
private String[] FileNameStrings = new String[8];
private File[] listFile;
@Override
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.capture_details);
Button buttonLoadImage = (Button) findViewById(R.id.btnBrowseimage);
buttonLoadImage.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View arg0)
Intent i = new Intent(
Intent.ACTION_PICK,
android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(i, RESULT_LOAD_IMAGE);
);
Button buttonLoadCamera = (Button) findViewById(R.id.btnCapture);
buttonLoadCamera.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View arg0)
// capture picture
try
Camera cam=new Camera();
fileUri= cam.captureImage();
catch (NullPointerException e)
e.printStackTrace();
//Toast.makeText(getBaseContext(), "Error:1 on uplod file", Toast.LENGTH_LONG).show();
catch (Exception e)
e.printStackTrace();
//Toast.makeText(getBaseContext(), "Error:2 File may be already exists", Toast.LENGTH_LONG).show();
);
Button buttonSendData = (Button) findViewById(R.id.btnSend);
buttonSendData.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View arg0)
new PostDataAsyncTask().execute();
);
Button buttonCancel = (Button) findViewById(R.id.btnCancel);
buttonCancel.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View arg0)
finish();
System.exit(0);
);
/**
* Checking GPS
* */
//locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
//Toast.makeText(getBaseContext(), "Gps turned on ", Toast.LENGTH_LONG).show();
/**/
//TelephonyManager mTelephonyMgr;
//mTelephonyMgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
//String myPhoneNumber = mTelephonyMgr.getLine1Number();
//myPhoneNumber.substring(2);
/**
* Checking GPS
* */
public void onLocationChanged(Location location)
String str = "Latitude: "+location.getLatitude()+" Longitude: "+location.getLongitude();
Toast.makeText(getBaseContext(), str, Toast.LENGTH_LONG).show();
public void onProviderDisabled(String provider)
Toast.makeText(getBaseContext(), "Gps turned off ", Toast.LENGTH_LONG).show();
public void onProviderEnabled(String provider)
Toast.makeText(getBaseContext(), "Gps turned on ", Toast.LENGTH_LONG).show();
/**/
/**
* Display image from a path to ImageView
*/
@SuppressLint("SdCardPath")
private void previewCapturedImage()
try
// bimatp factory
BitmapFactory.Options options = new BitmapFactory.Options();
// downsizing image as it throws OutOfMemory Exception for larger
options.inSampleSize = 8;
final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(), options);
//Saving captured image to sdcard/cers
String filaname= Get_next_file_name();
try
FileOutputStream out = new FileOutputStream(Environment.getExternalStorageDirectory() + File.separator + "cers"+ File.separator+ filaname+".jpg");
bitmap.compress(Bitmap.CompressFormat.PNG, 80, out);
out.close();
catch (Exception e)
e.printStackTrace();
//imgPreview.setImageBitmap(bitmap);
IMGS[0] = (ImageView) findViewById(R.id.imageViewphoto1);
IMGS[1] = (ImageView) findViewById(R.id.imageViewphoto2);
IMGS[2] = (ImageView) findViewById(R.id.imageViewphoto3);
IMGS[3] = (ImageView) findViewById(R.id.imageViewphoto4);
IMGS[4] = (ImageView) findViewById(R.id.imageViewphoto5);
IMGS[5] = (ImageView) findViewById(R.id.imageViewphoto6);
IMGS[6] = (ImageView) findViewById(R.id.imageViewphoto7);
IMGS[7] = (ImageView) findViewById(R.id.imageViewphoto8);
for(int i=0;i<8;i++)
if((String) IMGS[i].getTag()==null)
IMGS[i].setImageBitmap(bitmap);
File finalFile = new File(Environment.getExternalStorageDirectory() + File.separator + "cers"+ File.separator+ filaname+".jpg");
FileNameStrings[i]= new String(finalFile.getAbsolutePath().toString());
IMGS[i].setTag( "image" +i);
IMGS[i].getLayoutParams().height = 100;
IMGS[i].getLayoutParams().width = 100;
break;
catch (NullPointerException e)
e.printStackTrace();
public String Get_next_file_name()
int fn,ofn=0;
String[] filename;
// Check for SD Card
if (!Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED))
Toast.makeText(this, "Error! No SDCARD Found!", Toast.LENGTH_LONG).show();
else
// Locate the image folder in your SD Card
file = new File(Environment.getExternalStorageDirectory() + File.separator +"cers");
// Create a new folder if no folder named SDImageTutorial exist
file.mkdirs();
if (file.isDirectory())
listFile = file.listFiles();
for (int i = 0; i < listFile.length; i++)
filename =listFile[i].getName().split(".");
try
fn=Integer.parseInt(filename[0]);
if(ofn<fn)
ofn=fn;
ofn=ofn+1;
catch(Exception e)
e.printStackTrace();
StringBuilder sb = new StringBuilder();
sb.append("");
sb.append(ofn);
return sb.toString();
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
super.onActivityResult(requestCode, resultCode, data);
// if the result is capturing Image
if (requestCode == CAMERA_CAPTURE_IMAGE_REQUEST_CODE)
if (resultCode == RESULT_OK)
// successfully captured the image
// display it in image view
previewCapturedImage();
else if (resultCode == RESULT_CANCELED)
// user cancelled Image capture
Toast.makeText(getApplicationContext(),
"User cancelled image capture", Toast.LENGTH_SHORT)
.show();
else
// failed to capture image
Toast.makeText(getApplicationContext(),
"Sorry! Failed to capture image", Toast.LENGTH_SHORT)
.show();
// Browse Images
if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && null != data)
Uri selectedImage = data.getData();
String[] filePathColumn = MediaStore.Images.Media.DATA ;
Cursor cursor = getContentResolver().query(selectedImage, filePathColumn, null, null, null);
cursor.moveToFirst();
int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
String picturePath = cursor.getString(columnIndex);
cursor.close();
IMGS[0] = (ImageView) findViewById(R.id.imageViewphoto1);
IMGS[1] = (ImageView) findViewById(R.id.imageViewphoto2);
IMGS[2] = (ImageView) findViewById(R.id.imageViewphoto3);
IMGS[3] = (ImageView) findViewById(R.id.imageViewphoto4);
IMGS[4] = (ImageView) findViewById(R.id.imageViewphoto5);
IMGS[5] = (ImageView) findViewById(R.id.imageViewphoto6);
IMGS[6] = (ImageView) findViewById(R.id.imageViewphoto7);
IMGS[7] = (ImageView) findViewById(R.id.imageViewphoto8);
for(int i=0;i<8;i++)
if((String) IMGS[i].getTag()==null)
//IMGS[i].setImageBitmap(decodeSampledBitmapFromResource(getResources(), R.id.tempimage, 100, 100));
IMGS[i].setImageBitmap(BitmapFactory.decodeFile(picturePath));
File finalFile = new File(picturePath);
FileNameStrings[i]= new String(finalFile.getAbsolutePath().toString());
IMGS[i].setTag( "image" +i);
IMGS[i].getLayoutParams().height = 100;
IMGS[i].getLayoutParams().width = 100;
IMGS[i].setScaleType(ScaleType.FIT_CENTER);
break;
此处发生错误（相机类）
// start the image capture Intent
startActivityForResult(intent, CAMERA_CAPTURE_IMAGE_REQUEST_CODE);
这是相机类
package com.example.imagecapture;
import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.util.Log;
public class Camera extends Activity
private Uri fileUri;
private static final int CAMERA_CAPTURE_IMAGE_REQUEST_CODE = 100;
private static final int CAMERA_CAPTURE_VIDEO_REQUEST_CODE = 200;
public static final int MEDIA_TYPE_IMAGE = 1;
public static final int MEDIA_TYPE_VIDEO = 2;
private static final String IMAGE_DIRECTORY_NAME = "CERS";
/**
* @param args
*/
public static void main(String[] args)
// TODO Auto-generated method stub
public boolean DeviceSupportCamera()
if (!isDeviceSupportCamera())
return false;
else
return true;
/**
* Checking device has camera hardware or not
* */
public boolean isDeviceSupportCamera()
if (getApplicationContext().getPackageManager().hasSystemFeature(
PackageManager.FEATURE_CAMERA))
// this device has a camera
return true;
else
// no camera on this device
return false;
/**
* Capturing Camera Image will lauch camera app requrest image capture
*/
public Uri captureImage()
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);
intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);
// start the image capture Intent
startActivityForResult(intent, CAMERA_CAPTURE_IMAGE_REQUEST_CODE);
return fileUri;
/**
* Here we store the file url as it will be null after returning from camera
* app
*/
@Override
protected void onSaveInstanceState(Bundle outState)
super.onSaveInstanceState(outState);
// save file url in bundle as it will be null on scren orientation
// changes
outState.putParcelable("file_uri", fileUri);
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState)
super.onRestoreInstanceState(savedInstanceState);
// get the file url
fileUri = savedInstanceState.getParcelable("file_uri");
/**
* ------------ Helper Methods ----------------------
* */
/**
* Creating file uri to store image
*/
public Uri getOutputMediaFileUri(int type)
return Uri.fromFile(getOutputMediaFile(type));
/**
* returning image / video
*/
private static File getOutputMediaFile(int type)
// External sdcard location
File mediaStorageDir = new File(
Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
IMAGE_DIRECTORY_NAME);
// Create the storage directory if it does not exist
if (!mediaStorageDir.exists())
if (!mediaStorageDir.mkdirs())
Log.d(IMAGE_DIRECTORY_NAME, "Oops! Failed create "
+ IMAGE_DIRECTORY_NAME + " directory");
return null;
// Create a media file name
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",
Locale.getDefault()).format(new Date());
File mediaFile;
if (type == MEDIA_TYPE_IMAGE)
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "IMG_" + timeStamp + ".jpg");
else if (type == MEDIA_TYPE_VIDEO)
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "VID_" + timeStamp + ".mp4");
else
return null;
return mediaFile;
【问题讨论】：
在此处检查接受的答案：***.com/questions/5991319/… 【参考方案1】：您永远不应该创建 Activity 类的实例。检查 Raghav Sood 的答案
Can i Create the object of a activity in other class?
Camera cam=new Camera();
你有
public class Camera extends Activity
活动在清单中声明并具有生命周期。请改用startActivity 或startActivityForResult。
你也不需要
public static void main(String[] args)
// TODO Auto-generated method stub
将您的捕获图像代码移动到capture_image 并使用startActivityForResult。
【讨论】：
感谢您的回复。我尝试在 capture_image 活动中捕获图像代码。它的工作。但是我想把这2个分开。怎么做？ @SajithaRathnayake 如果您愿意，您可以在不同的活动中使用它，但使用startActivityForresult 并使用意图将路径传递回之前的活动。使用路径显示图片
如何使用 dialog.setMessage("上传文件"+ textFile);查看当前上传的文件？我试过了，但是出错了。
@SajithaRathnayake 是什么错误？如果您有完全不同的问题，请提出新问题
错误是“只有创建视图层次结构的原始线程才能接触它的视图。”【参考方案2】：
使用意图开始新课程。
Intent i = new Intent(capture_image.this, Camera.class);
startActivity(i);
或
startActivityForResult(i); // if you need to get back a result from Camera class
确保它在您的清单文件中声明。
【讨论】：
请指导我将这些代码放在哪里。请用我的代码给我看以上是关于如何从 Activity 调用一个类的主要内容，如果未能解决你的问题，请参考以下文章
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