如何创建一个android的react-native组件（二）

接着上一篇文章，这一篇我把自己上传到npm上的react-native-segmented-android开发步骤和大家分享。

下载react-native组件命令：

1	$ npm install react-native-segmented-android --save

这是效果图：

这次要实现的是View组件，所以要通过继承SimpleViewManager 来实现，步骤和（一）基本保持一致。

开始

Step 1 - 新建react-native工程 ReactNativeSegmentedAndroid

1	$ react-native init ReactNativeSegmentedAndroid

Step 2 - 将新建的工程导入android studio然后新建空library（以react-native-segmented-android为library的名称）

Step 3 - 新建空library（以react-native-segmented-android为library的名称）
在library目录下的build.gradle中添加react-native的依赖

// file: android/react-native-segmented-android/build.gradle
...

dependencies {
    ...
    compile 'info.hoang8f:android-segmented:1.0.6'
    compile 'com.facebook.react:react-native:0.16.+' 
}

Step 4 - 创建AndroidSegmented类继承SegmentedGroup

public class AndroidSegmented extends SegmentedGroup{


    public void setSegmentOrientation(String str){
        if(str.equals("horizontal")){
            setOrientation(RadioGroup.HORIZONTAL);
        }else if(str.equals("vertical")){
            setOrientation(RadioGroup.VERTICAL);
        }
    }


    public AndroidSegmented(ThemedReactContext context) {
        super(context);
        setGravity(Gravity.CENTER);

        setLayoutParams(new ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.WRAP_CONTENT,
                ViewGroup.LayoutParams.WRAP_CONTENT
        ));
    }

    private final Runnable mLayoutRunnable = new Runnable() {
        @Override
        public void run() {
            measure(MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.EXACTLY),
                    MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.EXACTLY));
            layout(getLeft(), getTop(), getRight(), getBottom());
        }
    };

    @Override
    public void requestLayout() {
        super.requestLayout();
        post(mLayoutRunnable);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);
    }

}

Step 5 - 继承SimpleViewManager，注意这时就不是继承ReactContextBaseJavaModule了，大家可以很明显的发现setChildText（）方法上多了一个‘@ReactProp(name = “childText”)’，加上了‘@ReactProp’的，segmented控件多了一个name为childText的属性，值为ReadableArray ( js端代码:childText={[‘One’,’Two’,’Three’,’Four’,”Five”]})。

public class AndroidSegmentedManager extends SimpleViewManager<AndroidSegmented> {

    public static final String REACT_CLASS = "AndroidSegmented";

    private static final String COLOR_REGEX = "^#([0-9A-Fa-f]{6}|[0-9A-Fa-f]{8})$";

    private Context context;

    @Override
    public String getName() {
        return REACT_CLASS;
    }

    @Override
    protected AndroidSegmented createViewInstance(ThemedReactContext reactContext) {
        this.context = reactContext;
        return new AndroidSegmented(reactContext);
    }



    @Override
    protected void addEventEmitters(final ThemedReactContext reactContext, final AndroidSegmented view) {
        view.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {


                int childCount = view.getChildCount();
                for (int i = 0; i < childCount; i++) {
                    ((RadioButton)view.getChildAt(i)).setChecked(false);
                    if (view.getChildAt(i).getId() == checkedId) {
                        ((RadioButton)view.getChildAt(i)).setChecked(true);
 
                        reactContext.getNativeModule(UIManagerModule.class).getEventDispatcher()
                                .dispatchEvent( 
                                        new AndroidSegmentedEvent( 
                                                view.getId(),
                                                SystemClock.uptimeMillis(),
                                                i));
                    } 
                } 


            }
        });


    }


    @ReactProp(name = "childText")
    public void setChildText(AndroidSegmented view, ReadableArray data) {
        int childCount = data.size();
        Log.e("TAG", "___" + childCount);

        for (int i = 0; i < childCount; i++) {
            RadioButton child = (RadioButton) LayoutInflater.from(context).inflate(R.layout.radio_button, null);

            child.setText(data.getString(i));
            view.addView(child);
        }
    }


    @ReactProp(name = "selectedPosition")
    public void setSelectedChild(AndroidSegmented view, int position) {
        RadioButton radioBt= (RadioButton)(view.getChildAt(position));
        radioBt.setChecked(true);
    }


    @ReactProp(name = "orientation")
    public void setOrientation(AndroidSegmented view, String orientation) {
        view.setSegmentOrientation(orientation);
    }


    @ReactProp(name = "tintColor")
    public void setTintColor(AndroidSegmented view, ReadableArray data) {

        String type0 = data.getType(0).name();
        String type1 = data.getType(1).name();

        if ("String".equals(type0) && "String".equals(type1)) {
            String color0 = data.getString(0);
            String color1 = data.getString(1);
            if (color0 != null && color1 != null) {
                if (color0.matches(COLOR_REGEX) && color1.matches(COLOR_REGEX)) {

                    view.setTintColor(Color.parseColor(color0), Color.parseColor(color1));
                } else {
                    throw new JSApplicationIllegalArgumentException("Invalid arrowColor property: " + color0);
                }
            }
        }
    }
}

Step 6 - 创建AndroidSegmentedEvent类继承Event

public class AndroidSegmentedEvent extends Event<AndroidSegmentedEvent> {

    public static final String EVENT_NAME = "topChange";
    private final int selectedPosition;

    public AndroidSegmentedEvent(int viewId, long timestampMs, int selectedPosition) {
        super(viewId, timestampMs);
        this.selectedPosition = selectedPosition;
    }


    @Override
    public String getEventName() {
        return EVENT_NAME;
    }

    @Override
    public void dispatch(RCTEventEmitter rctEventEmitter) {
        rctEventEmitter.receiveEvent(getViewTag(), getEventName(), serializeEventData());

    }


    @Override
    public short getCoalescingKey() {
        return 0;
    }

    private WritableMap serializeEventData() {
        WritableMap eventData = Arguments.createMap();
        eventData.putInt("selected", getPosition());
        Log.e("AAA","position="+getPosition());

        return eventData;
    }

    private int getPosition() {
        return selectedPosition;
    }
}

Step 7 - 继承ReactPackage，注意createNativeModules（）返回的是加入了 AndroidToastModule 的集合，createJSModules（）与createViewManagers（）返回的都是空集合，如果Step 4 步继承的是BaseViewManager或其子类，那么createViewManagers（）中返回的就是加入了BaseViewManager的集合，其他的就是空集合，一般情况createJSModules（）的返回值都是空集合。

public class AndroidSegmentedPackage implements ReactPackage {

    @Override
    public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
        return Collections.emptyList();
    }

    @Override
    public List<Class<? extends JavaScriptModule>> createJSModules() {
        return Collections.emptyList();
    }

    @Override
    public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
        return Arrays.<ViewManager>asList(new AndroidSegmentedManager());
    }
}

Step 8 - 新建AndroidSegmented.js，文件位置
‘ android/react-native-segmented-android/AndroidSegmented.js ’代码如下，然后在 ‘android/react-native-segmented-android/’下运行如下命令生成package.json文件

1	$ npm init //生成package.json文件

//AndroidSegmented.js
'use strict';

var React = require('react-native');
var { requireNativeComponent, PropTypes, View } = React;

var NativeAndroidSegmented = requireNativeComponent('AndroidSegmented', AndroidSegmented);

class AndroidSegmented extends React.Component {
  constructor() {
    super();
    this._onChange = this._onChange.bind(this);
  }

  _onChange(event) {
    if (this.props.onChange) {
      this.props.onChange(event.nativeEvent);
    }
  }

  render() {
    return (
      <NativeAndroidSegmented
        {...this.props} 
        onChange={this._onChange}/>
    );
  }
}

var colorType = function (props, propName, componentName) {
  var checker = function() {
    var color = props[propName];
    var regex = /^#([0-9A-Fa-f]{6}|[0-9A-Fa-f]{8})$/;
    if (!regex.test(color)) {
      return new Error('Only accept color formats: #RRGGBB and #AARRGGBB');
    }
  };

  return PropTypes.string(props, propName, componentName) || checker();
}

AndroidSegmented.propTypes = {
  ...View.propTypes,
  childText: PropTypes.arrayOf(PropTypes.oneOfType([ PropTypes.string ])),
  orientation:PropTypes.string,
  tintColor:PropTypes.arrayOf(PropTypes.oneOfType([ PropTypes.string ])),
  selectedPosition:PropTypes.number,
  onChange: PropTypes.func,
}

AndroidSegmented.defaultProps = {
  
};

module.exports = AndroidSegmented;

//package.json内容
{
  "name": "react-native-segmented-android",
  "version": "1.0.3",
  "description": "a high imitation of iOS segmented Controls",
  "main": "AndroidSegmented.js",
  "scripts": {
    "test": "react-native start"
  },
  "repository": {
    "type": "git",
    "url": "https://github.com/zzyyppqq/react-native-segmented-android.git"
  },
  "keywords": [
    "android",
    "segmented",
    "react-component",
    "react-native"
  ],
  "author": "zzyyppqq",
  "license": "ISC",
  "peerDependencies": {
    "react-native": "^1.0.3"
  }
}

Step 9 - 复制AndroidSegmented.js 文件到‘/ReactNativeSegmentedAndroid/ ’ 目录下，如下是index.android.js代码，然后运行测试

'use strict';

var React = require('react-native');
var {
  AppRegistry,
  StyleSheet,
  Text,
  Dimensions,
  ToastAndroid,
  View,
} = React;

//var AndroidSegmented = require('react-native-segmented-android');
var AndroidSegmented = require('./AndroidSegmented');
var deviceWidth = Dimensions.get('window').width;
var deviceHeight = Dimensions.get('window').height;

var ReactNativeSegmentedExample = React.createClass({
  onSelectPosition:function(event){
    console.log(event);
    ToastAndroid.show('segment '+event.selected, ToastAndroid.SHORT)
  },
  render: function() {
    return (
      <View>
          <AndroidSegmented
            tintColor={['#ff0000','#ffffff']}
            style={{width:deviceWidth,height:60,backgroundColor:'#fff000',
                  justifyContent: 'center',
                  alignItems: 'center'}}
            childText={['One','Two','Three','Four',"Five"]}
            orientation='horizontal'
            selectedPosition={0}
            onChange={this.onSelectPosition} />

            <AndroidSegmented
              tintColor={['#009688','#ffffff']}
              style={{width:deviceWidth,height:200,backgroundColor:'#fff000',
                    justifyContent: 'center',
                    alignItems: 'center'}}
              childText={['One','Two','Three','Four',"Five"]}
              orientation='vertical'
              selectedPosition={0}
              onChange={this.onSelectPosition} />
        </View>
    );
  }
});

Install

Step 1 - Install the npm package

1	$ npm install react-native-degment-android --save

Step 2 - Update Gradle Settings

// file: android/settings.gradle
...

include ':react-native-degment-android', ':app'
project(':react-native-degment-android').projectDir = new File(rootProject.projectDir,'../node_modules/react-native-degment-android')

Step 3 - Update app Gradle Build

// file: android/app/build.gradle
...

dependencies {
    ...
    compile project(':react-native-degment-android')
}

Step 4 - Register React Package

...
import com.higo.zhangyp.segmented.AndroidSegmentedPackage; // <-- import

public class MainActivity extends FragmentActivity implements DefaultHardwareBackBtnHandler {

    private ReactInstanceManager mReactInstanceManager;
    private ReactRootView mReactRootView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mReactRootView = new ReactRootView(this);
        mReactInstanceManager = ReactInstanceManager.builder()
                .setApplication(getApplication())
                .setBundleAssetName("index.android.bundle")
                .setJSMainModuleName("index.android")
                .addPackage(new MainReactPackage())
                .addPackage(new AndroidSegmentedPackage()) // <-- Register package here
                .setUseDeveloperSupport(BuildConfig.DEBUG)
                .setInitialLifecycleState(LifecycleState.RESUMED)
                .build();
        mReactRootView.startReactApplication(mReactInstanceManager, "AwesomeProject", null);
        setContentView(mReactRootView);
    }
...

从react-native的官方文档中我们已经知道facebook的react-native团队已经为我们实现了很多组件，例如 Image、Text、ViewPagerAndroid等，我们在index.android.js中可以直接使用这些组件，这些组件为什么能直接使用呢？

大家会很自然的想到已经封装好了呗。那在哪封装的？如何封装的？其实只要通过命令react-native init ProjectName创建过react-native工程的同学来说，在哪儿封装的一目了然。我们来看react-native工程的结构图：

react-native工程中，在node_modules下有一个很特别的react-native文件夹，android的工程中的build.gradle 文件多了一个依赖，不用想肯定在这两个地方封装的，这也是react-native的关键。

1
2
3

dependencies {    
      compile 'com.facebook.react:react-native:0.16.+'   
 }

首先我们从入口MainActivity开始，看了我的前两篇文章，如何自定义react-native的android组件（一）和（二），要使用一个自定义组件，必须在MainActivity中加入【.addPackage(new AndroidSegmentedPackage()) 】才能使用。

...
  @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mReactRootView = new ReactRootView(this);

        mReactInstanceManager = ReactInstanceManager.builder()
                .setApplication(getApplication())
                .setBundleAssetName("index.android.bundle")
                .setJSMainModuleName("index.android")
                .addPackage(new MainReactPackage())
                .addPackage(new AndroidSegmentedPackage())  
                .setUseDeveloperSupport(BuildConfig.DEBUG)
                .setInitialLifecycleState(LifecycleState.RESUMED)
                .build();

        mReactRootView.startReactApplication(mReactInstanceManager, "ReactNativeSegmented", null);

        setContentView(mReactRootView);
    }
...

那么官方的Android组件是如何实现的呢，我们肯定注意到了【.addPackage(new MainReactPackage())】和自定义的是不是很像，格式也一样，我想肯定在这里面有实现，进入MainReactPackage类中，代码如下：

//react-native 源码
public class MainReactPackage implements ReactPackage {

  @Override
  public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
    return Arrays.<NativeModule>asList(
      new AsyncStorageModule(reactContext),
      new FrescoModule(reactContext),
      new IntentModule(reactContext),
      new LocationModule(reactContext),
      new NetworkingModule(reactContext),
      new WebSocketModule(reactContext),
      new ToastModule(reactContext));
  }

  @Override
  public List<Class<? extends JavaScriptModule>> createJSModules() {
    return Collections.emptyList();
  }

  @Override
  public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
    return Arrays.<ViewManager>asList(
      new ReactDrawerLayoutManager(),
      new ReactHorizontalScrollViewManager(),
      new ReactImageManager(),
      new ReactProgressBarViewManager(),
      new ReactRawTextManager(),
      new ReactScrollViewManager(),
      new ReactSwitchManager(),
      new ReactTextInputManager(),
      new ReactTextViewManager(),
      new ReactToolbarManager(),
      new ReactViewManager(),
      new ReactViewPagerManager(),
      new ReactTextInlineImageViewManager(),
      new ReactVirtualTextViewManager(),
      new SwipeRefreshLayoutManager());
  }
}

看了MainReactPackage中的代码，果不其然，首先我们看createViewManagers（）方法中的集合，看看集合子集的命名是不是很熟悉，
看看这里一共实现了多少原生控件：DrawerLayout、HorizontalScrollView、HorizontalScrollView、Image等等，还有SwipeRefreshLayout官网上还没有更新这个组件，其实这个版本已经可以使用了。

1.public class ReactDrawerLayoutManager extends ViewGroupManager<ReactDrawerLayout>
2.public class ReactImageManager extends SimpleViewManager<ReactImageView>
3.public class ReactProgressBarViewManager extends BaseViewManager<ProgressBarContainerView, ProgressBarShadowNode>
...

//贴上一个ReactDrawerLayoutManager源码，大家看看实现
public class ReactDrawerLayoutManager extends ViewGroupManager<ReactDrawerLayout> {

  private static final String REACT_CLASS = "AndroidDrawerLayout";

  public static final int OPEN_DRAWER = 1;
  public static final int CLOSE_DRAWER = 2;

  @Override
  public String getName() {
    return REACT_CLASS;
  }

  @Override
  protected void addEventEmitters(ThemedReactContext reactContext, ReactDrawerLayout view) {
    view.setDrawerListener(
        new DrawerEventEmitter(
            view,
            reactContext.getNativeModule(UIManagerModule.class).getEventDispatcher()));
  }

  @Override
  protected ReactDrawerLayout createViewInstance(ThemedReactContext context) {
    return new ReactDrawerLayout(context);
  }

  @ReactProp(name = "drawerPosition", defaultInt = Gravity.START)
  public void setDrawerPosition(ReactDrawerLayout view, int drawerPosition) {
    if (Gravity.START == drawerPosition || Gravity.END == drawerPosition) {
      view.setDrawerPosition(drawerPosition);
    } else {
      throw new JSApplicationIllegalArgumentException("Unknown drawerPosition " + drawerPosition);
    }
  }

  @ReactProp(name = "drawerWidth", defaultFloat = Float.NaN)
  public void getDrawerWidth(ReactDrawerLayout view, float width) {
    int widthInPx = Float.isNaN(width) ?
        ReactDrawerLayout.DEFAULT_DRAWER_WIDTH : Math.round(PixelUtil.toPixelFromDIP(width));
    view.setDrawerWidth(widthInPx);
  }

  @Override
  public boolean needsCustomLayoutForChildren() {
    // Return true, since DrawerLayout will lay out it's own children.
    return true;
  }

  @Override
  public @Nullable Map<String, Integer> getCommandsMap() {
    return MapBuilder.of("openDrawer", OPEN_DRAWER, "closeDrawer", CLOSE_DRAWER);
  }

  @Override
  public void receiveCommand(
      ReactDrawerLayout root,
      int commandId,
      @Nullable ReadableArray args) {
    switch (commandId) {
      case OPEN_DRAWER:
        root.openDrawer();
        break;
      case CLOSE_DRAWER:
        root.closeDrawer();
        break;
    }
  }

  @Override
  public @Nullable Map getExportedViewConstants() {
    return MapBuilder.of(
        "DrawerPosition",
        MapBuilder.of("Left", Gravity.START, "Right", Gravity.END));
  }

  @Override
  public @Nullable Map getExportedCustomDirectEventTypeConstants() {
    return MapBuilder.of(
        DrawerSlideEvent.EVENT_NAME, MapBuilder.of("registrationName", "onDrawerSlide"),
        DrawerOpenedEvent.EVENT_NAME, MapBuilder.of("registrationName", "onDrawerOpen"),
        DrawerClosedEvent.EVENT_NAME, MapBuilder.of("registrationName", "onDrawerClose"),
        DrawerStateChangedEvent.EVENT_NAME, MapBuilder.of(
            "registrationName", "onDrawerStateChanged"));
  }

  /**
   * This method is overridden because of two reasons:
   * 1. A drawer must have exactly two children
   * 2. The second child that is added, is the navigationView, which gets panned from the side.
   */
  @Override
  public void addView(ReactDrawerLayout parent, View child, int index) {
    if (getChildCount(parent) >= 2) {
      throw new
          JSApplicationIllegalArgumentException("The Drawer cannot have more than two children");
    }
    if (index != 0 && index != 1) {
      throw new JSApplicationIllegalArgumentException(
          "The only valid indices for drawer's child are 0 or 1. Got " + index + " instead.");
    }
    parent.addView(child, index);
    parent.setDrawerProperties();
  }

  public static class DrawerEventEmitter implements DrawerLayout.DrawerListener {

    private final DrawerLayout mDrawerLayout;
    private final EventDispatcher mEventDispatcher;

    public DrawerEventEmitter(DrawerLayout drawerLayout, EventDispatcher eventDispatcher) {
      mDrawerLayout = drawerLayout;
      mEventDispatcher = eventDispatcher;
    }

    @Override
    public void onDrawerSlide(View view, float v) {
      mEventDispatcher.dispatchEvent(
          new DrawerSlideEvent(mDrawerLayout.getId(), SystemClock.uptimeMillis(), v));
    }

    @Override
    public void onDrawerOpened(View view) {
      mEventDispatcher.dispatchEvent(
        new DrawerOpenedEvent(mDrawerLayout.getId(), SystemClock.uptimeMillis()));
    }

    @Override
    public void onDrawerClosed(View view) {
      mEventDispatcher.dispatchEvent(
          new DrawerClosedEvent(mDrawerLayout.getId(), SystemClock.uptimeMillis()));
    }

    @Override
    public void onDrawerStateChanged(int i) {
      mEventDispatcher.dispatchEvent(
          new DrawerStateChangedEvent(mDrawerLayout.getId(), SystemClock.uptimeMillis(), i));
    }
  }
}

原生控件的实现步骤、方法、例子等其实在源码中都有了，想实现什么组件就照着源码开发，绝不会出错啦。

到此只是完成了android端的java代码，那么组件如何与js代码联系起来，并且供js代码调用呢，我们来看看工程中的react-navie文件夹吧，秘密都在它里面。
react-navie文件结构：

打开react-native文件夹，我一眼就注意到了ReactAndroid目录（因为做Android嘛，对含有Android的词比较敏感>_<），翻遍了其下所有的目录文件，终于找到一个有用点的文件package.json，在其中找到关键的一句话
【”main”: “Libraries/react-native/react-native.js”】图上用红框标注了。
下一步就该看看Libraries目录了，Libraries目录结构：