Class與class
假如把class看做是一張圖紙的話，那根據圖紙加工出來的零件就是一個個的instance（實例）。那你有沒有想過，實際上一張具體的圖紙也可以看過是某個類型的實例呢？每張圖紙是不是都有標題？有作者？有創作日期？是不是存在一個“類”專門來描述它？答案是，有，就是Class！
class是描述對象的，Class是用來描述類的。獲取Class
MyObject mObj = new MyObject();
Class clazz = mObj.getClass();
Class clazz2 = Class.forName("com.jeremy.reflection.MyObject ");
- 使用Class
- 實例化對象
Class clazz = Class.forName("com.jeremy.universal_android.reflection.MyObject");
//通過無參構造函數實例化對象
MyObject object = (MyObject) clazz.newInstance();
- 調用其他構造函數
public class MyObject {
final String TAG = "MyObject";
String name;
int index;
public MyObject() {
this.name = "default";
this.index = 0;
}
public MyObject(String str) {
this.name = str;
this.index = 0;
}
public MyObject(String str, int i) {
this.name = str;
this.index = i;
}
public void print() {
LogTool.e(TAG, "name --> " + name + ",index --> " + index);
}
public void printWithParam(String str) {
LogTool.e(TAG, "printWithParam --> " + str);
}
}
MyObject object;
Class clazz = Class.forName("com.jeremy.universal_android.reflection.MyObject");
Constructor<?> constructors[] = clazz.getConstructors();
object = (MyObject) constructors[0].newInstance();
object.print();
object = (MyObject) constructors[1].newInstance("My name is Obj");
object.print();
object = (MyObject) constructors[2].newInstance("My name is Obj", 100);
object.print();
結果為
E/MyObject: name --> default,index --> 0
E/MyObject: name --> My name is Obj,index --> 0
E/MyObject: name --> My name is Obj,index --> 100
- 獲取實現的接口
public class MyObject implements Interface1, Interface2 {
}
Class<?> interfaces[] = clazz.getInterfaces();
for (int i = 0; i < interfaces.length; i++) {
LogTool.e(TAG, interfaces[i].getName());
}
E/MyObject: com.jeremy.universal_android.reflection.Interface1
E/MyObject: com.jeremy.universal_android.reflection.Interface2
- 獲得父類
Class<?> parents = clazz.getSuperclass();
LogTool.e(TAG, parents.getName());
結果
E/MyObject: java.lang.Object
- 獲得完整構造函數的簽名
StringBuilder method;
Constructor<?> con;
Constructor<?> cons[] = clazz.getConstructors();
for (int i = 0; i < cons.length; i++) {
method = new StringBuilder();
con = cons[i];
// 獲取修飾符
int modifier = con.getModifiers();
method.append(Modifier.toString(modifier));
// 獲取構造函數名稱
method.append(" ").append(con.getName());
method.append("(");
// 獲取構造函數參數類型
Class<?> params[] = con.getParameterTypes();
for (int j = 0; j < params.length; ++j) {
method.append(params[j].getName() + " arg" + i);
if (j < params.length - 1) {
method.append(",");
}
}
method.append("){}");
LogTool.e(TAG, method.toString());
}
結果
E/MyObject: public com.jeremy.universal_android.reflection.MyObject(){}
E/MyObject: public com.jeremy.universal_android.reflection.MyObject(java.lang.String arg1){}
E/MyObject: public com.jeremy.universal_android.reflection.MyObject(java.lang.String arg2,int arg2){}
- 獲得本類屬性
Field field = null;
StringBuilder fieldDes = null;
//獲得本類屬性
Field[] fields = clazz.getDeclaredFields();
//獲得父類屬性
//Field[] fields = clazz.getFields();
for (int i = 0; i < fields.length; i++) {
fieldDes = new StringBuilder();
field = fields[i];
// 獲取修飾符
int modifier = field.getModifiers();
fieldDes.append(Modifier.toString(modifier));
Class<?> type = field.getType();
fieldDes.append(" " + type.getName() + " " + field.getName());
LogTool.e(TAG, fieldDes.toString());
}
結果
E/MyObject: public final java.lang.String TAG
E/MyObject: public java.lang.String name
E/MyObject: public int index
- 通過反射調用方法
//通過反射調用方法
Method method1 = clazz.getMethod("print");
method1.invoke(clazz.newInstance());
//調用有參數的方法
method1 = clazz.getMethod("printWithParam", String.class);
method1.invoke(clazz.newInstance(), "hello world");
結果
E/MyObject: name --> default,index --> 0
E/MyObject: printWithParam --> hello world
