二维码（生成二维码和扫描二维码）

例：

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26

    allprojects {
        repositories {
            jcenter()
            maven { url "https://jitpack.io" }
        }
    }

    defaultConfig {
        applicationId "com.example.day_0524_zxing"
        minSdkVersion 16
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

    }
    allprojects {
        repositories {
            jcenter()
            maven { url "https://jitpack.io" }
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'

    compile 'com.github.open-android:Zxing:v1.0.3'
}

加个依赖

dependencies {
    compile 'com.github.open-android:Zxing:v1.0.3'
}

android {

    allprojects {
        repositories {
            jcenter()
            maven { url "https://jitpack.io" }
        }
    }

}

加权限：

<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.FLASHLIGHT" />

MainActivity 主方法类：

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private EditText mContent;
    private Button mCreate,mScan;
    private ImageView mImage;
    private final static int REQ_CODE = 1028;
    private TextView mHint;
    private TextView mResult;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }
    private void initView() {
        mContent = (EditText)findViewById(R.id.edt_content);
        mCreate = (Button)findViewById(R.id.btn_create);
        mScan = (Button)findViewById(R.id.btn_scan);

        mImage = (ImageView)findViewById(R.id.iv_image);
        mHint = (TextView)findViewById(R.id.tv_hint);
        mResult = (TextView)findViewById(R.id.tv_result);

        mCreate.setOnClickListener(this);
        mScan.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            
            case R.id.btn_create :
                //生成二维码
                String content = mContent.getText().toString().trim();
                Bitmap bitmap = null;
                try {
                    bitmap = BitmapUtils.create2DCode(content);
                    mImage.setVisibility(View.VISIBLE);
                    mHint.setVisibility(View.GONE);
                    mImage.setImageBitmap(bitmap);
                }catch (Exception e) {
                    e.printStackTrace();
                }
                break;
                
            case R.id.btn_scan :
                //扫码
                Intent intent = new Intent(MainActivity.this, CaptureActivity.class);
                startActivityForResult(intent,REQ_CODE);
                break;
            default:
                break;
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == REQ_CODE) {
            mImage.setVisibility(View.VISIBLE);
            mContent.setVisibility(View.GONE);

            String result = data.getStringExtra(CaptureActivity.SCAN_QRCODE_RESULT);
            Bitmap bitmap = data.getParcelableExtra(CaptureActivity.SCAN_QRCODE_BITMAP);

            mResult.setText("扫描结果为：" + result);
            showToast("扫码结果："+result);
            if (bitmap != null) {
                mImage.setImageBitmap(bitmap);
            }
        }
    }

    private void showToast(String msg) {
        Toast.makeText(MainActivity.this, "" + msg, Toast.LENGTH_SHORT).show();
    }
}

activity_main布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <EditText
        android:id="@+id/edt_content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入内容" />
    <Button
        android:id="@+id/btn_create"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="生成二维码" />
    <Button
        android:id="@+id/btn_scan"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="扫码（支持识别相册二维码）" />
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp">
        <ImageView
            android:id="@+id/iv_image"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:visibility="gone" />
        <TextView
            android:id="@+id/tv_hint"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:text="扫描返回bitmap"
            android:textColor="#f00" />
    </RelativeLayout>
    <TextView
        android:id="@+id/tv_result"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#ffff00"/>
</LinearLayout>