我试图找出控制器继承的工作原理。我有三个控制器：
package com.example.praduman.humlog;
import java.io.Serializable;
/**
* Created by Praduman on 23/07/2015.
*/
public class HumLogController implements Serializable{
private transient HumLogModel humLogModel;
private transient String username;
private transient String password;
public transient String userType;
public HumLogController() {
this.humLogModel = new HumLogModel();
}
public void createNewUser(){
humLogModel.createNewUser("TestUser4", "1234");
}
}
The log cat is ...
07-26 15:07:23.785 8885-8885/? D/dalvikvm﹕ Late-enabling CheckJNI
07-26 15:07:23.805 8885-8891/? D/dalvikvm﹕ Debugger has detached; object registry had 1 entries
07-26 15:07:23.905 8885-8888/? D/dalvikvm﹕ GC_CONCURRENT freed 201K, 3% free 8981K/9212K, paused 2ms+0ms, total 7ms
07-26 15:07:23.909 8885-8900/? I/dalvikvm﹕ Could not find method android.database.Cursor.getNotificationUri, referenced from method com.parse.ParseSQLiteCursor.getNotificationUri
07-26 15:07:23.909 8885-8900/? W/dalvikvm﹕ VFY: unable to resolve interface method 489: Landroid/database/Cursor;.getNotificationUri ()Landroid/net/Uri;
07-26 15:07:23.909 8885-8900/? D/dalvikvm﹕ VFY: replacing opcode 0x72 at 0x0002
07-26 15:07:23.913 8885-8885/? I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getChangingConfigurations, referenced from method android.support.v7.internal.widget.TintTypedArray.getChangingConfigurations
07-26 15:07:23.913 8885-8885/? W/dalvikvm﹕ VFY: unable to resolve virtual method 441: Landroid/content/res/TypedArray;.getChangingConfigurations ()I
07-26 15:07:23.913 8885-8885/? D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
07-26 15:07:23.921 8885-8885/? I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getType, referenced from method android.support.v7.internal.widget.TintTypedArray.getType
07-26 15:07:23.921 8885-8885/? W/dalvikvm﹕ VFY: unable to resolve virtual method 463: Landroid/content/res/TypedArray;.getType (I)I
07-26 15:07:23.921 8885-8885/? D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
07-26 15:07:23.925 8885-8885/? I/dalvikvm﹕ Could not find method android.content.res.Resources.getDrawable, referenced from method android.support.v7.internal.widget.ResourcesWrapper.getDrawable
07-26 15:07:23.925 8885-8885/? W/dalvikvm﹕ VFY: unable to resolve virtual method 404: Landroid/content/res/Resources;.getDrawable (ILandroid/content/res/Resources$Theme;)Landroid/graphics/drawable/Drawable;
07-26 15:07:23.929 8885-8885/? D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
07-26 15:07:23.929 8885-8885/? I/dalvikvm﹕ Could not find method android.content.res.Resources.getDrawableForDensity, referenced from method android.support.v7.internal.widget.ResourcesWrapper.getDrawableForDensity
07-26 15:07:23.929 8885-8885/? W/dalvikvm﹕ VFY: unable to resolve virtual method 406: Landroid/content/res/Resources;.getDrawableForDensity (IILandroid/content/res/Resources$Theme;)Landroid/graphics/drawable/Drawable;
07-26 15:07:23.929 8885-8885/? D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
07-26 15:07:23.997 8885-8888/? D/dalvikvm﹕ GC_CONCURRENT freed 268K, 4% free 9101K/9396K, paused 1ms+2ms, total 8ms
07-26 15:07:24.057 8885-8885/? D/AndroidRuntime﹕ Shutting down VM
07-26 15:07:24.057 8885-8885/? W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xa4c3e648)
07-26 15:07:24.057 8885-8885/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.praduman.humlog/com.example.praduman.humlog.LogInActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.praduman.humlog.HumLogController.createNewUser(HumLogController.java:18)
at com.example.praduman.humlog.LogInActivity.onCreate(LogInActivity.java:23)
at android.app.Activity.performCreate(Activity.java:5133)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
和我的观点
var myApp = angular.module('app', []);
myApp.controller('MainController', ['$scope', function($scope) {
$scope.name = 'main';
$scope.getName = function() {
return $scope.name;
};
}]);
myApp.controller('Child1', ['$scope', function($scope) {
$scope.name = 'child1';
}]);
myApp.controller('Child2', ['$scope', function($scope) {
$scope.name = 'child2';
}]);
但他们都显示“主要”。我该如何解决这个问题？
答案 0 :(得分：2)
Here's an example如何在Angular中扩展控制器。
myApp.service('baseCtrl', function () {
this.name = 'base';
this.getName = function() {
return this.name;
};
});
myApp.controller('MainController', ['baseCtrl', function (baseCtrl) {
angular.extend(this, baseCtrl);
this.name = 'main';
}]);
myApp.controller('Child1', ['baseCtrl', function (baseCtrl) {
angular.extend(this, baseCtrl);
this.name = 'child1';
}]);
myApp.controller('Child2', ['baseCtrl', function (baseCtrl) {
angular.extend(this, baseCtrl);
this.name = 'child2';
}]);
它必须使用controllerAs，将$scope替换为this，这对于此类情况特别有用。
注意service而不是其他Angular服务类型的使用，它使用了new，因此可以将this...语句从控制器带到单独的服务。
有几种方法可以进行控制器继承。这是another approach。
关于原始代码，Angular中没有'controller iheritance'。并且$scope原型继承假设
$scope.getName = function() {
return $scope.name;
};
从定义它的上下文返回$scope.name，在你的情况下它是MainController函数。
答案 1 :(得分：1)
您面临的问题实际上是基于核心Javascript功能。
你知道，你所面临的困惑源于范围界定和原型继承的混合。复制属性，但范围保持不变，阻止您访问您希望能够访问的变量。要更好地理解这一点，也许可以代替$scope，我们可以看一个更简单的变量：
myApp.controller('MainController', ['$scope', function($scope) {
var a = 1;
$scope.getName = function() {
console.log(a); // -> 1
console.log(b); // Error! `Uncaught ReferenceError: b is not defined`
};
}]);
myApp.controller('Child1', ['$scope', function($scope) {
var b = 2;
}]);
显然，MainController并不知道Child1定义了一个名为b的变量，因此它出错了。该变量严格超出词汇范围。
同样，如果我们将b重命名为a，则无法将MainController中的值转换为2.这可以准确地说明了您的具体情况：你有三个叫$scope的东西，只有一个在词法范围内。
修复它的两个选项：
1）使用this：
$scope.getName = function() {
return this.name;
};
this解决方案的工作原理是因为Javascript如何确定＆＃34;这个＆＃34;基于背景。基本上，由于它附加到给定的$scope对象，因此该对象是一个很好的候选对象。但是Mozilla可以比我更好地解释这一点，所以在这里查看关于这个主题的页面：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this
2）否则，您只需传递$scope：
$scope.getName = function(item) {
return item.name;
};
答案 2 :(得分：0)
如果要覆盖子范围中的name属性，请将原始名称属性转换为object。
$scope.user = {};
$scope.user.name='main';
$scope.getName = function() {
return $scope.user.name;
};
您应该阅读https://github.com/angular/angular.js/wiki/Understanding-Scopes了解详细信息。