android怎么对二维码解码

在Android中，可以使用ZXing库来对二维码进行解码。下面是详细的步骤：

1. 添加依赖库：在项目级别的build.gradle文件中添加以下代码：

```

allprojects {

repositories {

...

mavenCentral()

}

}

```

在模块级别的build.gradle文件中添加以下代码：

```

dependencies {

...

implementation 'com.google.zxing:core:3.4.1'

implementation 'com.journeyapps:zxing-android-embedded:4.2.0'

}

```

2. 创建扫描界面：在layout文件夹下创建一个新的xml文件，命名为activity_scan.xml，添加以下代码：

```xml

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical">

android:id="@+id/result_text_view"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Scan Result"

android:textSize="18sp"

android:textStyle="bold"

android:layout_marginTop="16dp"

android:layout_marginBottom="16dp"

android:layout_gravity="center_horizontal" />

android:id="@+id/preview_surface_view"

android:layout_width="match_parent"

android:layout_height="0dp"

android:layout_weight="1" />

```

3. 创建扫描Activity：创建一个新的java类，命名为ScanActivity，并继承自AppCompatActivity。添加以下代码：

```java

import android.Manifest;

import android.content.Intent;

import android.content.pm.PackageManager;

import android.os.Bundle;

import android.support.annotation.Nullable;

import android.support.v4.app.ActivityCompat;

import android.support.v4.content.ContextCompat;

import android.support.v7.app.AppCompatActivity;

import android.util.Log;

import android.view.SurfaceHolder;

import android.view.SurfaceView;

import android.widget.TextView;

import android.widget.Toast;

import com.google.zxing.DecodeHintType;

import com.google.zxing.integration.android.IntentIntegrator;

import com.google.zxing.integration.android.IntentResult;

import com.journeyapps.barcodescanner.BarcodeCallback;

import com.journeyapps.barcodescanner.BarcodeResult;

import com.journeyapps.barcodescanner.DecoratedBarcodeView;

import com.journeyapps.barcodescanner.DefaultDecoderFactory;

import java.util.Arrays;

import java.util.Collection;

import java.util.HashMap;

import java.util.Map;

public class ScanActivity extends AppCompatActivity implements

ActivityCompat.OnRequestPermissionsResultCallback {

private static final String TAG = ScanActivity.class.getSimpleName();

private DecoratedBarcodeView barcodeView;

private TextView resultTextView;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_scan);

barcodeView = findViewById(R.id.barcode_view);

resultTextView = findViewById(R.id.result_text_view);

// 设置解码格式

Collection formats = Arrays.asList(BarcodeFormat.QR_CODE);

barcodeView.getBarcodeView().setDecoderFactory(new DefaultDecoderFactory(formats));

// 设置回调

barcodeView.decodeContinuous(callback);

}

private BarcodeCallback callback = new BarcodeCallback() {

@Override

public void barcodeResult(BarcodeResult result) {

if (result.getText() != null) {

barcodeView.setStatusText(result.getText());

resultTextView.setText(result.getText());

}

}

@Override

public void possibleResultPoints(List resultPoints) {

}

};

@Override

protected void onResume() {

super.onResume();

// 请求相机权限

if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)

!= PackageManager.PERMISSION_GRANTED) {

ActivityCompat.requestPermissions(this,

new String[]{Manifest.permission.CAMERA}, 0);

} else {

barcodeView.resume();

}

}

@Override

protected void onPause() {

super.onPause();

barcodeView.pause();

}

@Override

public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {

super.onRequestPermissionsResult(requestCode, permissions, grantResults);

if (requestCode == 0) {

if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

barcodeView.resume();

} else {

Toast.makeText(this, "Camera permission denied", Toast.LENGTH_SHORT).show();

}

}

}

}

```

4. 在AndroidManifest.xml中注册扫描Activity：

```xml

package="com.example.qrcodedecode">

...

android:name=".ScanActivity"

android:label="Scan QR Code">

...

```

5. 启动扫描界面：在MainActivity中添加以下代码，以启动扫描界面：

```java

import android.content.Intent;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

public class MainActivity extends AppCompatActivity {

private Button startScanButton;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

startScanButton = findViewById(R.id.start_scan_button);

startScanButton.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

Intent intent = new Intent(MainActivity.this, ScanActivity.class);

startActivity(intent);

}

});

}

}

```

现在运行应用程序，点击"Start Scan"按钮即可启动二维码扫描界面，扫描二维码后会把解码结果显示在界面上的TextView中。