Android CameraX Turn on camera preview function

The goal is very simple. Use CameraX to open the camera preview and display it on the interface in real time. See if CameraX is as useful as Google says. First click the simplest one to display the preview.

Introduce dependencies

Some configurations of module gradle use Android SDK version 31, databinding is enabled

apply plugin: ''
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-kapt'

android {
    compileSdkVersion 31
    buildToolsVersion "31.0.0"
    defaultConfig {
        minSdkVersion 21
        targetSdkVersion 31
    }
    dataBinding {
        enabled = true
    }
}

Introduced CameraX dependencies (CameraX core library is implemented with camera2), currently mainly using version 1.1.0-alpha11

dependencies {
    implementation ":camera-core:1.1.0-alpha11"
    implementation ":camera-camera2:1.1.0-alpha11"
    implementation ":camera-lifecycle:1.1.0-alpha11"
    implementation ":camera-view:1.0.0-alpha31"
    implementation ":camera-extensions:1.0.0-alpha31"
}

Using the CameraX core library in version 1.0.2 will report an error and cannot be foundgetOrCreateInstancemethod.

??? bug "NoSuchMethodError getOrCreateInstance"

```log
CrashHandler: In thread: Thread[main,5,main]
    UncaughtException detected: : No static method getOrCreateInstance(Landroid/content/Context;)Lcom/google/common/util/concurrent/ListenableFuture; in class Landroidx/camera/core/CameraX; or its super classes (declaration of '' appears in /data/app/.tutorial2020-1/)
    at (:149)
    at .(:36)
    at (:6161)
    at (:1112)
    at (:2507)
    at (:2640)
    at $800(:182)
    at $(:1493)
    at (:111)
    at (:194)
    at (:5682)
    at (Native Method)
    at (:372)
    at $(:963)
    at (:758)
```

Permissions

Need to apply dynamicallyPermissions

<uses-permission android:name="" />

This article skips the places where dynamic application permissions are applied

interface

CameraX has prepared for developers with thoughtfulness

Put it in a FrameLayout, as shown below act_simple_preivew_x.layout

<?xml version="1.0" encoding="utf-8"?>
<layout>
    <FrameLayout xmlns:andro
        android:
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <
            android:
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </FrameLayout>
</layout>

Turn on preview

Turn on camera preview in activity

// 
import ;

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import ;
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import ;
import ;
import ;
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import ;
import ;

import ;
// import .;
// import .;

import ;

public class SimplePreviewXAct extends AppCompatActivity {

    private ActSimplePreivewXBinding mBinding;
    private ListenableFuture&lt;ProcessCameraProvider&gt; cameraProviderFuture;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        (savedInstanceState);
        mBinding = (this, .act_simple_preivew_x);
        cameraProviderFuture = (this);
        (() -&gt; {
            try {
                ProcessCameraProvider cameraProvider = ();
                bindPreview(cameraProvider);
            } catch (ExecutionException | InterruptedException e) {
                // No need to deal with it here            }
        }, (this));
    }

    void bindPreview(@NonNull ProcessCameraProvider cameraProvider) {
        Preview preview = new ().build();

        CameraSelector cameraSelector = new ()
                .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                .build();

        (());

        Camera camera = (this, cameraSelector, preview);
    }
}

Note that we are using

To obtain ProcessCameraProvider, useMethod to get onecameraProviderFuture。
existcameraProviderFutureRemove ProcessCameraProvider after completion (cameraProvider）。

To enable preview,Build a Preview. Use CameraSelector to select the rear camera.
Preview's SurfaceProvider is provided by the layout.

After binding, start the camera preview

Run the test

Run it to your phone, open this Activity and you can see the camera preview. The aspect ratio of the image is normal and there is no stretching phenomenon.

Honor EMUI 3.1 Lite, Android 5.1 is running normally
Redmi 9A, MIUI 12.5.1 stable version, Android 10 runs normally
OnePlus 5, H2OS 10.0.3, Android 10 is running normally

Add switch

Add 2 buttons to the layout to control the camera switch

&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;layout&gt;

    &lt;LinearLayout xmlns:andro
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"&gt;

        &lt;LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/colorPrimaryDark"
            android:gravity="center"
            android:orientation="horizontal"
            android:padding="4dp"&gt;

            &lt;Button
                android:
                style="@style/NormalBtn"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Open" /&gt;

            &lt;Button
                android:
                style="@style/NormalBtn"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginStart="12dp"
                android:text="closure" /&gt;
        &lt;/LinearLayout&gt;

        &lt;FrameLayout xmlns:andro
            android:
            android:layout_width="match_parent"
            android:layout_height="match_parent"&gt;

            &lt;
                android:
                android:layout_width="match_parent"
                android:layout_height="match_parent" /&gt;
        &lt;/FrameLayout&gt;

    &lt;/LinearLayout&gt;
&lt;/layout&gt;

Change the root layout to LinearLayout

RevisebindPreviewMethod, first check whether the incoming ProcessCameraProvider is empty

private void bindPreview(ProcessCameraProvider cameraProvider) {
    if (cameraProvider == null) {
        (getApplicationContext(), "No camera was obtained", Toast.LENGTH_SHORT).show();
        return;
    }
    Preview preview = new ().build();

    CameraSelector cameraSelector = new ()
            .requireLensFacing(CameraSelector.LENS_FACING_BACK)
            .build();

    (());

    Camera camera = (this, cameraSelector, preview);
}

Modified activity part code

import ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;

import ;
// import .;
// import .;

import ;

public class SimplePreviewXAct extends AppCompatActivity {

    private ActSimplePreivewXBinding mBinding;
    private ListenableFuture&lt;ProcessCameraProvider&gt; mCameraProviderFuture;
    private ProcessCameraProvider mCameraProvider;
    private boolean mRunning = false;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        (savedInstanceState);
        mBinding = (this, .act_simple_preivew_x);
        mCameraProviderFuture = (this);
        (() -&gt; {
            try {
                mCameraProvider = ();
            } catch (ExecutionException | InterruptedException e) {
                // No need to deal with it here            }
        }, (this));
        (v -&gt; {
            if (mCameraProvider != null &amp;&amp; !mRunning) {
                bindPreview(mCameraProvider);
            }
        });
        (v -&gt; {
            ();
            mRunning = false;
        });
    }

    private void bindPreview(ProcessCameraProvider cameraProvider) {
        if (cameraProvider == null) {
            (getApplicationContext(), "No camera was obtained", Toast.LENGTH_SHORT).show();
            return;
        }
        Preview preview = new ().build();

        CameraSelector cameraSelector = new ()
                .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                .build();

        (());

        Camera camera = (this, cameraSelector, preview);
        mRunning = true;
    }
}

Get itmCameraProviderDo not bind the life cycle immediately afterwards.

If you want to enable preview, callbindPreview(mCameraProvider). Record that the camera has now been turned onmRunning = true。

If you want to stop previewing, unbind your life cycle(). This method needs to be called in the main thread.

After running, you can use buttons to control the switch for the camera preview. Compared to before, the height of the PreviewView has become a little smaller (let the point position to the button).
However, the video's aspect ratio is normal and it is not stretched. Under the default configuration, there is also the function of autofocus.

summary

Judging from the simple camera preview, CameraX simplifies the work of developers. Provides a PreviewView, developers do not need to customize itSurfaceView or TextureView. In real-time preview, the camera can focus automatically. This article uses 1.1.0-alpha11, while CameraX is still in development.

refer to

camerax implementation preview -

/jetpack/androidx/releases/camera

NoSuchMethodError - *

Original linkCameraX Turn on camera preview

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