Android 显示相机界面

Question

我正在尝试制作一个将用于拍照的应用程序，因此我创建了一个 Android Studio 项目，空白 activity 并尝试放置来自 [=15= 的代码] 的开发者页面 MainActivity.java，但是无论我把代码放在哪里，我都无法让运行的应用程序显示相机界面。

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    /** A safe way to get an instance of the Camera object. */
    public static Camera getCameraInstance(){
        Camera c = null;
        try {
            c = Camera.open(); // attempt to get a Camera instance
        }
        catch (Exception e){
            // Camera is not available (in use or does not exist)
        }
        return c; // returns null if camera is unavailable
    }
    
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

Answer 1

要显示相机，您需要先征得用户的同意。在开发者页面中明确提到 here 。示例代码将是这样的

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import android.Manifest;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;


public class MainActivity extends AppCompatActivity {

private static final int MY_PERMISSIONS_REQUEST_CAMERA = 1;
Camera mCamera;
CameraPreview mPreview;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
    Button btnCamera = findViewById(R.id.camera);

    if (ContextCompat.checkSelfPermission(getApplicationContext(),
            Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {

        if (ActivityCompat.shouldShowRequestPermissionRationale((this)
                , Manifest.permission.CAMERA)) {

        } else {
            ActivityCompat.requestPermissions((this),
                    new String[]{Manifest.permission.CAMERA},
                    MY_PERMISSIONS_REQUEST_CAMERA);
        }

    }
    btnCamera.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            mCamera  = getCameraInstance();
            // Create our Preview view and set it as the content of our activity.
            mPreview = new CameraPreview(getApplicationContext(), mCamera);
            preview.addView(mPreview);
        }
    });

}
public static Camera getCameraInstance() {
    Camera c = null;
    try {
        c = Camera.open(); // attempt to get a Camera instance
    } catch (Exception e) {
        // Camera is not available (in use or does not exist)
    }
    return c;
}}

这是布局示例

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:text="Camera"
    android:id="@+id/camera"/>

<FrameLayout
    android:id="@+id/camera_preview"
    android:layout_width="fill_parent"
    android:layout_height="match_parent" />

</LinearLayout>

Android 显示相机界面

Android Display Camera Interface

android

android-camera