我一直关注以下tutorial，它使用移动视觉API创建条形码/二维码扫描程序。虽然我输入了它所说的确切代码（至少我认为），相机来自cameraSource。
我在这个过程中添加了一些额外的代码，看它是否会有所作为，但它仍然没有。问题是，当我启动应用程序时，SurfaceView应显示CAMERA_FACING_BACK Feed，但它是纯黑色。如果你能告诉我为什么饲料没有出现，如果有，需要改变的代码，将非常感激。
MainActivity.java：
package com.example.neekondev.barcodeshortened;
import android.Manifest;
import android.content.pm.PackageManager;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.util.SparseArray;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.TextView;
import com.google.android.gms.vision.CameraSource;
import com.google.android.gms.vision.Detector;
import com.google.android.gms.vision.barcode.Barcode;
import com.google.android.gms.vision.barcode.BarcodeDetector;
import java.io.IOException;
import static com.google.android.gms.vision.CameraSource.CAMERA_FACING_BACK;
import static com.google.android.gms.vision.CameraSource.CAMERA_FACING_FRONT;
public class MainActivity extends AppCompatActivity {
SurfaceView cameraView;
TextView barcodeInfo;
BarcodeDetector barcodeDetector;
CameraSource cameraSource;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cameraView = (SurfaceView) findViewById(R.id.camera_view);
barcodeInfo = (TextView) findViewById(R.id.code_info);
barcodeDetector =
new BarcodeDetector.Builder(this)
.setBarcodeFormats(Barcode.CODE_39 | Barcode.CODE_93 | Barcode.CODE_128)
.build();
cameraSource = new CameraSource
.Builder(this, barcodeDetector)
.setRequestedPreviewSize(640, 480)
.setRequestedFps(20.0f)
.setFacing(CAMERA_FACING_BACK)
.build();
cameraView.getHolder().addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceCreated(SurfaceHolder holder) {
try {
if (ActivityCompat.checkSelfPermission(getApplicationContext(),
Manifest.permission.CAMERA) !=
PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
cameraSource.start(cameraView.getHolder());
} catch (IOException ie) {
Log.e("CAMERA SOURCE", ie.getMessage());
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height)
{
}
@Override
public void surfaceDestroyed(SurfaceHolder holder)
{
cameraSource.stop();
}
});
barcodeDetector.setProcessor(new Detector.Processor<Barcode>() {
@Override
public void release() {
}
@Override
public void receiveDetections(Detector.Detections<Barcode> detections) {
final SparseArray<Barcode> barcodes = detections.getDetectedItems();
if (barcodes.size() != 0) {
barcodeInfo.post(new Runnable() { // Use the post method of the TextView
public void run() {
barcodeInfo.setText( // Update the TextView
barcodes.valueAt(0).displayValue
);
}
});
}
}
});
}
}
activity_main.xml中：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.neekondev.barcodeshortened.MainActivity">
<SurfaceView
android:layout_width="640px"
android:layout_height="480px"
android:layout_centerVertical="true"
android:layout_alignParentLeft="true"
android:id="@+id/camera_view"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/code_info"
android:layout_toRightOf="@+id/camera_view"
android:textSize="20sp"
android:layout_marginLeft="16dp"
android:text="Nothing yet..."
android:layout_alignParentTop="true"
/>
</RelativeLayout>
的manifest.xml：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.neekondev.barcodeshortened">
<meta-data android:name="com.google.android.gms.vision.DEPENDENCIES" android:value="barcode"/>
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.Camera"/>
<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：4)
没关系，我自己想出来了，虽然我认为其他人可能会在教程之后提出同样的问题，所以我会告诉你出了什么问题。你看，虽然我在Manifest中声明了权限，android.permissions.CAMERA是一个＆＃34;高风险权限＆＃34;，这意味着用户需要在它可能被激励之前手动同意它。因为我从未创建过权限对话框来直接向用户请求，所以使用相机权限的所有代码都无法执行，从而为我们提供了空白屏幕与相机的提要。一个简单的解决方法是进入设置并允许其中的权限，但可以使用以下代码，方便地通过对话框请求相机权限;
import android.Manifest;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.media.Image;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.util.SparseArray;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.TextView;
import com.google.android.gms.vision.CameraSource;
import com.google.android.gms.vision.Detector;
import com.google.android.gms.vision.barcode.Barcode;
import com.google.android.gms.vision.barcode.BarcodeDetector;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import java.io.IOException;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Date;
import static junit.framework.Assert.assertNotNull;
public class MainActivity
extends AppCompatActivity {
FirebaseDatabase database;
DatabaseReference myRef;
SurfaceView cameraView;
TextView barcodeInfo;
BarcodeDetector barcodeDetector;
CameraSource cameraSource;
private static final int CAMERA_PERMISSION_CAMERA = 0x000000;
public static boolean position = false;
//Camera cam;
//Camera.Parameters p;
@Override
protected void onCreate(Bundle savedInstanceState) {
setRequestedOrientation(ActivityInfo
.SCREEN_ORIENTATION_PORTRAIT);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (ContextCompat.checkSelfPermission(MainActivity
.this,
Manifest
.permission
.CAMERA)
!= PackageManager
.PERMISSION_GRANTED) {
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity
.this,
Manifest
.permission
.CAMERA)) {
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
} else {
// No explanation needed, we can request the permission.
ActivityCompat.requestPermissions(MainActivity
.this,
new String[]{Manifest.permission
.CAMERA},
CAMERA_PERMISSION_CAMERA);
// CAMERA_PERMISSION_CAMERA is an
// app-defined int constant. The callback method gets the
// result of the request.
}
}
cameraView = (SurfaceView) findViewById(R
.id
.camera_view);
barcodeInfo = (TextView) findViewById(R
.id
.code_info);
MainActivity
.this
.getPackageManager()
.hasSystemFeature
(PackageManager
.FEATURE_CAMERA_FLASH);
barcodeDetector =
new BarcodeDetector.Builder(getApplicationContext())
.setBarcodeFormats(Barcode.ALL_FORMATS)
.build();
cameraSource = new CameraSource
.Builder(getApplicationContext(), barcodeDetector)
.setFacing(CameraSource.CAMERA_FACING_BACK)
.setRequestedFps(35.0f)
.setRequestedPreviewSize(960, 960)
.setAutoFocusEnabled(true)
.build();
//setupButtons();
cameraView.getHolder().addCallback(new SurfaceHolder
.Callback() {
@Override
public void surfaceCreated(SurfaceHolder holder) {
try {
if (ActivityCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.CAMERA)
!= PackageManager.PERMISSION_GRANTED) {
// TODO: CONSIDER CALLING
//ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
cameraSource.start(cameraView
.getHolder());
} catch (IOException ie) {
Log.e("CAMERA SOURCE", ie
.getMessage());
}
}
@Override
public void surfaceChanged(SurfaceHolder holder,
int format,
int width,
int height){}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
cameraSource.stop();
}
});
barcodeDetector.setProcessor(new Detector.Processor<Barcode>()
{
@Override
public void release() {
}
@Override
public void receiveDetections(Detector.Detections<Barcode> detections)
{
final SparseArray<Barcode> barcodes = detections.getDetectedItems();
database = FirebaseDatabase.getInstance();
myRef = database
.getReference(getTime());
if (barcodes
.size() != 0) {
barcodeInfo
.post(new Runnable() { // Use the post method of the TextView
public void run() {
barcodeInfo.setText(barcodes
.valueAt(0)
.displayValue
);
myRef.setValue(barcodes
.valueAt(0)
.displayValue
);
}
});
}
}
});
}
/*
public void FLASH_ON()
{
cam = Camera.open();
p = cam.getParameters();
p.setFlashMode(Camera
.Parameters
.FLASH_MODE_TORCH);
cam.setParameters(p);
cam.startPreview();
}
public void FLASH_OFF()
{cam.stopPreview();
cam.release();}
public void setupButtons()
{
ImageButton flash = (ImageButton)findViewById(R.id.flash);
flash.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v)
{
if (position == false)
{
FLASH_ON();
position = true;
} if (position == true)
{
FLASH_OFF();
position = false;
}
}
});
}*/
public String getTime()
{
String downToSeconds = DateFormat
.getDateTimeInstance()
.format(
new Date());
return downToSeconds;
}
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[],
int[] grantResults) {
switch (requestCode) {
case CAMERA_PERMISSION_CAMERA: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0]
== PackageManager
.PERMISSION_GRANTED) {
Intent startMain = new Intent(MainActivity
.this, MainActivity
.class);
startActivity(startMain);
} else {
if (ContextCompat.checkSelfPermission(MainActivity
.this,
Manifest
.permission
.CAMERA)
!= PackageManager
.PERMISSION_GRANTED) {
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity
.this,
Manifest
.permission
.CAMERA)) {
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
} else {
// No explanation needed, we can request the permission.
ActivityCompat.requestPermissions(MainActivity
.this,
new String[]{Manifest.permission
.CAMERA},
CAMERA_PERMISSION_CAMERA);
// CAMERA_PERMISSION_CAMERA is an
// app-defined int constant. The callback method gets the
// result of the request.
}
}
}
return;
}
}
}
}
请原谅我的一些服务器代码。我也将结果上传到firebase数据库。其余的是相同的。布局有一些小的调整用于缩放，但其余的是相同的。祝你好运！