Android开发学习之路--Camera之初体验

顾名思义Camera就是拍照和录像的功能，像微信里面，我们想拍照传一下照片，就可以通过camera来拍照，然后存储照片，发送给好友。那么微信的app里面是不会直接通过camera api来实现的，因为系统一般都会有camera这个程序，那么直接调用camera app来实现拍照的功能不是很方便嘛，这里我们学习下。其实最终camera调用到android底层的是v4l2的接口，关于v4l2，还有android的camera的框架以后有机会再好好研究研究。

调用系统自带的camera需要用到intent，通过MediaStore获取照片路径，下面来试一下，新建工程CameraPictureTest，为layout添加代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_margin="10dp">

<ImageView
android:id="@+id/picture"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>

<Button
android:id="@+id/take_photo"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="拍照"/>

</LinearLayout>

编写代码如下：

package com.example.jared.camerapicturetest;

import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

public static final int TAKE_PHOTO = 1;
public static final int CROP_PICTURE = 2;

private Button takePhoto;
private ImageView picture;
private Uri imageUri;

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

takePhoto = (Button)findViewById(R.id.take_photo);
takePhoto.setOnClickListener(new myOnClickListener());

picture = (ImageView)findViewById(R.id.picture);
picture.setOnClickListener(new myOnClickListener());
}

private class myOnClickListener implements View.OnClickListener {
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.take_photo:
setTakePhoto();
break;
default:
break;
}
}
}

public void setTakePhoto() {
File outputImage = new File(Environment.getExternalStorageDirectory(), "test.jpg");
try {
if(outputImage.exists()) {
outputImage.delete();
}
outputImage.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
imageUri = Uri.fromFile(outputImage);
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
startActivityForResult(intent, TAKE_PHOTO);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
switch (requestCode) {
case TAKE_PHOTO:
if(resultCode == RESULT_OK) {
Intent intent1 = new Intent("com.android.camera.action.CROP");
intent1.setDataAndType(imageUri, "image/*");
intent1.putExtra("scale", true);
intent1.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
startActivityForResult(intent1, CROP_PICTURE);
}
break;
case CROP_PICTURE:
if(resultCode == RESULT_OK) {
try {
Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver()
.openInputStream(imageUri));
picture.setImageBitmap(bitmap);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
break;
default:
break;
}
}
}

这里首先确定了保存的路径为根目录下的test.jpg，然后通过intent，传入这个路径的Uri，打开相机进行拍照，这里有对拍照的返回，如果返回成功，那么就调用CROP的功能对照片进行裁剪，进入到裁减后返回成功就把图片显示在layout创建的ImageView中。

具体需要真机显示，这里再插播一段关于真机屏幕在mac电脑上的显示，具体可以参考这篇文章，将你的安卓手机屏幕共享到PC或Mac上。通过一个chrome的Vysor插件来实现，需要android的5.0以上的版本才可以。

好了，下面看下显示的效果：







效果基本上出来了，很不错的插件。微信里面很多不是直接拍照发送的，还有通过选择相册的图片，已经拍好的照片来发送图片的，那么接着我们来实现这个功能，首先layout添加了choosephoto：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_margin="10dp">

<ImageView
android:id="@+id/picture"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>

<Button
android:id="@+id/take_photo"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="拍照"/>

<Button
android:id="@+id/choose_photo"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="选取照片"/>
</LinearLayout>

接着修改MainActivity代码如下：

package com.example.jared.camerapicturetest;

import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

public static final int TAKE_PHOTO = 1;
public static final int CROP_PICTURE = 2;

private Button takePhoto;
private Button choosePhoto;
private ImageView picture;
private Uri imageUri;

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

takePhoto = (Button)findViewById(R.id.take_photo);
takePhoto.setOnClickListener(new myOnClickListener());

choosePhoto = (Button)findViewById(R.id.choose_photo);
choosePhoto.setOnClickListener(new myOnClickListener());

picture = (ImageView)findViewById(R.id.picture);
picture.setOnClickListener(new myOnClickListener());
}

private class myOnClickListener implements View.OnClickListener {
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.take_photo:
setTakePhoto();
break;
case R.id.choose_photo:
setChoosePhoto();
default:
break;
}
}
}

public void setChoosePhoto() {
File outputImage1 = new File(Environment.getExternalStorageDirectory(), "test1.jpg");
try {
if(outputImage1.exists()) {
outputImage1.delete();
}
outputImage1.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
imageUri = Uri.fromFile(outputImage1);
Intent intent1 = new Intent("android.intent.action.GET_CONTENT");
intent1.setType("image/*");
intent1.putExtra("crop", true);
intent1.putExtra("scale", true);
intent1.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
startActivityForResult(intent1, CROP_PICTURE);

}

public void setTakePhoto() {
File outputImage = new File(Environment.getExternalStorageDirectory(), "test.jpg");
try {
if(outputImage.exists()) {
outputImage.delete();
}
outputImage.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
imageUri = Uri.fromFile(outputImage);
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
startActivityForResult(intent, TAKE_PHOTO);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
switch (requestCode) {
case TAKE_PHOTO:
if(resultCode == RESULT_OK) {
Intent intent1 = new Intent("com.android.camera.action.CROP");
intent1.setDataAndType(imageUri, "image/*");
intent1.putExtra("scale", true);
intent1.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
startActivityForResult(intent1, CROP_PICTURE);
}
break;
case CROP_PICTURE:
if(resultCode == RESULT_OK) {
try {
Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver()
.openInputStream(imageUri));
picture.setImageBitmap(bitmap);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
break;
default:
break;
}
}
}

基本上和拍照也差不多，然后我们运行下看看效果：







点击选择照片按钮，我们会进入到相册的app里面，然后选择一张照片，然后裁剪后保存，如上图所示。

附：参考《第一行代码》