Android Studio - QR code scanning
===

* [name=Ander Liu]

###### tags: `Android Studio`

[TOC]

## Zxing
* **ZXing** ("zebra crossing") is an open-source, multi-format 1D/2D barcode image processing library implemented in Java, with ports to other languages.
* 這堂課，我們打算使用 **Zxing** 這個 library to implement QR code scanning
* The Supported Formats of **Zxing**

| 1D product | 1D industrial | 2D |
| ---------- | ------------- | -------------- |
| UPC-A | Code 39 | QR Code |
| EAN-8 | Code 128 | Aztec (beta) |
| EAN-13 | Codabar | PDF 417 (beta) |
| | ITF | MaxiCode |
| | RSS-14 | |
| | RSS-Expanded | |
* [Official APP on Google Play](https://play.google.com/store/apps/details?id=com.google.zxing.client.android)
* 我們基本上是根據此網站來設置
https://github.com/journeyapps/zxing-android-embedded

## Adding dependency with Gradle
:::danger
Android SDK 需要 19 以上
:::
* 我們先把 library 加進來
* 開啟 **build.gradle**，在適當的位置加入以下 dependency

dependencies {
    implementation 'com.journeyapps:zxing-android-embedded:3.6.0'
    implementation 'com.android.support:appcompat-v7:25.3.1'   // Minimum 23+ is required
}


## Hardware Acceleration
* Hardware accelation is required since [`TextureView`](https://developer.android.com/reference/android/view/TextureView) is used
* 開啟 **AndroidManifest.xml**，在適當的位置 enable hardwareAccelerated 屬性

<application android:hardwareAccelerated="true" ... >

## Usage with IntentIntegrator
* 此為 the source code of the `IntentIntegrator`
https://github.com/journeyapps/zxing-android-embedded/blob/master/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java
* `IntentIntegrator`顧名思義，就是 [`intent`](https://developer.android.com/reference/android/content/Intent)的integrate版。可以call一些method來設定要開啟的掃描acticity的屬性，最後 call [`initiateScan()`](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L258)來開啟掃描acticity
:::warning
有關 [`intent`](https://developer.android.com/reference/android/content/Intent)，之後會再介紹
:::
* 以下為可能會用到的 method
* 第 98 行 [IntentIntegrator(Activity activity)](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L98) `the Constructor`
* 第 146 行 [IntentIntegrator forFragment(Fragment fragment)](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L146)
* 第 167 行 [IntentIntegrator setPrompt(String prompt)](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L167) `Set a prompt to display on the capture screen, instead of using the default.`
* 第 179 行 [IntentIntegrator setOrientationLocked(boolean locked)](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L179) `By default, the orientation is locked. Set to false to not lock.`
* 第 189 行 [IntentIntegrator setCameraId(int cameraId)](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L189) `Use the specified camera ID.`
* 第 214 行 [IntentIntegrator setBeepEnabled(boolean enabled)](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L214) `Set to false to disable beep on scan.`
* 第 225 行 [IntentIntegrator setBarcodeImageEnabled(boolean enabled)](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L225) `Set to true to enable saving the barcode image and sending its path in the result Intent.`
* 第 247 行 [IntentIntegrator setDesiredBarcodeFormats(String... desiredBarcodeFormats)](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L247) `Set the desired barcode formats to scan.`
* 第 258 行 [void initiateScan()](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L258) `Initiates a scan for all known barcode types with the default camera.`

new IntentIntegrator(this).initiateScan(); // \`this\` is the current Activity

// Get the results:
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    IntentResult result = IntentIntegrator.parseActivityResult(requestCode, resultCode, data);
    if(result != null) {
        if(result.getContents() == null) {
            Toast.makeText(this, "Cancelled", Toast.LENGTH_LONG).show();
        } else {
            Toast.makeText(this, "Scanned: " + result.getContents(), Toast.LENGTH_LONG).show();
        }
    } else {
        super.onActivityResult(requestCode, resultCode, data);
    }
}

* 第 1 行，[`initiateScan()`](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L258)，用來啟動掃描Activity，可以寫在 onClick() 或是 onCreate() 等等method裡面
* 第 3-16行，[`onActictyResult()`](https://developer.android.com/reference/android/app/Activity#onActivityResult(int,%20int,%20android.content.Intent))，目的是取得掃描Activity傳回來的結果，不需要動這部分，直接貼到 **MainActivity.java** 即可
:::warning
有關*啟動 Activity 以取得結果*，之後會再介紹
:::
* result.getContents() 為結果，如果打算顯示掃描結果，複製結果，開啟URL，便需要利用此結果

### Customize options
* 此為其他客製化功能，和 [`initiateScan()`](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L258)一樣，寫在 onClick() 或是 onCreate() 等等method裡面

IntentIntegrator integrator = new IntentIntegrator(this);
integrator.setDesiredBarcodeFormats(IntentIntegrator.QR_CODE);
integrator.setPrompt("Scan a QR code");
integrator.setCameraId(0);  // Use a specific camera of the device
integrator.setBeepEnabled(false);
integrator.setBarcodeImageEnabled(true);
integrator.initiateScan();

### Changing the orientation
1. 開啟 **AndroidManifest.xml**，加入以下code

<activity
        android:name="com.journeyapps.barcodescanner.CaptureActivity"
        android:screenOrientation="fullSensor"
        tools:replace="screenOrientation" />


2. [`setOrientationLocked()`](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L179) set false to not lock，和 [`initiateScan()`](https://github.com/journeyapps/zxing-android-embedded/blob/6556f815584f921e21bb088d2f6423baa99d0547/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java#L258)寫在一起

IntentIntegrator integrator = new IntentIntegrator(this);
integrator.setOrientationLocked(false);
integrator.initiateScan();

## Button and Text display
1. layout 如下所示

2. 在 **MainActivity.java** 寫一個 onClick() method，裡面放剛剛的那些code

public void onClick(View view){   
    IntentIntegrator integrator = new IntentIntegrator(this);  
    integrator.setOrientationLocked(false);  
    integrator.setDesiredBarcodeFormats(IntentIntegrator.QR_CODE);  
    integrator.setPrompt("Scan a QR code");  
    integrator.setCameraId(0); // Use a specific camera of the device  
    integrator.setBeepEnabled(false);  
    integrator.setBarcodeImageEnabled(true);  
    integrator.initiateScan();
}

3. 在 [`onActictyResult()`](https://developer.android.com/reference/android/app/Activity#onActivityResult(int,%20int,%20android.content.Intent))裡面加入第 4 行和第 12 行，用 [`TextView`](https://developer.android.com/reference/android/widget/TextView)顯示結果

// Get the results:  
@Override  
protected void onActivityResult(int requestCode, int resultCode, Intent data) {  
    TextView textView = findViewById(R.id.textView);
  
    IntentResult result = IntentIntegrator.parseActivityResult(requestCode, resultCode, data);  
    if(result != null) {  
        if(result.getContents() == null) {  
            Toast.makeText(this, "Cancelled", Toast.LENGTH_LONG).show();  
        } else {  
            Toast.makeText(this, "Scanned: " \+ result.getContents(), Toast.LENGTH_LONG).show();  
            textView.setText(result.getContents());  
        }  
    } else {  
        super.onActivityResult(requestCode, resultCode, data);  
    }  
}

4. 把 onClick() 設置到 button 上

:::success
Done!!!
:::

## Reference
* [Github | Zxing](https://github.com/journeyapps/zxing-android-embedded)
* [Github | IntentIntegrator.java](https://github.com/journeyapps/zxing-android-embedded/blob/master/zxing-android-embedded/src/com/google/zxing/integration/android/IntentIntegrator.java)
* [Useful Reference](http://lmgtfy.com/?q=Android+QR+code)

## Future feature
* Scan a photo
* [Copy to clipboard](https://developer.android.com/guide/topics/text/copy-paste#java)
* Open the URL link

## Homepage
* [Homepage](/@NDR/Homepage)

*[SDK]: Software Development Kit
*[URL]: Uniform Resource Locator