Question

我想在循环中创建新的Runnable。但是，不可能在内部类中使用变量。我不能使用global / instance变量，因为它会产生错误的结果。我的程序类似于以下简化代码：

public class RunManager {
    public void runManager(int delay, final Context context) {
        for (int dim = 7; dim < 227; dim++) {
            Runnable r = new Runnable() {
                @Override
                public void run() {
                    RandomKernels randomKernels = new RandomKernels();
                    try {
                        randomKernels.foo(context, dim);
                    } catch (InterruptedException e) {
                        Log.e(tag, e.getMessage());
                    }
                }
            };
            Thread cnnThread = new Thread(r);
            cnnThread.start();
            try {
                Thread.sleep(delay);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

错误是：Variable 'dim' is accessed from within inner class, needs to be declared final.

Answer 1

您的问题是您正在尝试从新线程访问非最终变量。为了从新线程中加入变量，需要将其声明为final。在你的cas中，你可以将dim int复制到大小为1的final int数组，然后从线程访问该数组。

Answer 2

可能最简单的方法是为Runnable创建一个接受int作为参数的构造函数。如：

public class MyRunnable implements Runnable {

   public MyRunnable(Context context, int dim) {
       // save parameters as class variables
   }

   public void run() {
       // do the work
   }
}

然后叫它：

Runnable r = new MyRunnable(context, dim);
new Thread(r).start();

Answer 3

如果您想要访问内部类中的值，则应使用final int[] dim。

public class RunManager {

    public void runManager(int delay, final Context context) {
        for (final int dim[] = {7}; dim[1] < 227; dim[1]++) {
            Runnable r = new Runnable() {
                @Override
                public void run() {
                    RandomKernels randomKernels = new RandomKernels();
                    try {
                        randomKernels.foo(context, dim[1]);
                    } catch (InterruptedException e) {
                        Log.e(tag, e.getMessage());
                    }
                }
            };
            Thread cnnThread = new Thread(r);
            cnnThread.start();
            try {
                Thread.sleep(delay);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

选项2 - 使用字段：

public class RunManager {

    private int _dim;

    public void runManager(int delay, final Context context) {
        for (int dim = 7; dim < 227; dim++) {
            _dim = dim;
            Runnable r = new Runnable() {
                @Override
                public void run() {
                    RandomKernels randomKernels = new RandomKernels();
                    try {
                        randomKernels.foo(context, _dim);
                    } catch (InterruptedException e) {
                        Log.e(tag, e.getMessage());
                    }
                }
            };
            Thread cnnThread = new Thread(r);
            cnnThread.start();
            try {
                Thread.sleep(delay);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

选项3 - 在另一个方法中迭代并添加final int dim作为方法参数：

private void createThreads(int delay, final Object context) {
    for (int dim = 7; dim < 227; dim++) {
        runManager(delay, context, dim);
    }
}

public void runManager(int delay, final Context context, final int dim) {
    Runnable r = new Runnable() {
        @Override
        public void run() {
            RandomKernels randomKernels = new RandomKernels();
            try {
                randomKernels.foo(context, dim);
            } catch (InterruptedException e) {
                Log.e(tag, e.getMessage());
            }
        }
    };
    Thread cnnThread = new Thread(r);
    cnnThread.start();
    try {
        Thread.sleep(delay);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

选项4 - 使用自定义runnable。您可以按照@BMacedo的建议实现类，也可以在内部类中创建抽象类和实现逻辑。

public class RunManager {

    public void runManager(int delay, final Context context) {
        for (int dim = 7; dim < 227; dim++) {
            CustomRunnable r = new CustomRunnable() {
                private int _dim;

                @Override
                public void run() {
                    RandomKernels randomKernels = new RandomKernels();
                    try {
                        randomKernels.foo(context, _dim);
                    } catch (InterruptedException e) {
                        Log.e(tag, e.getMessage());
                    }
                }

                public void setDim(int dim) {
                    _dim = dim;
                }
            };

            r.setDim(dim);

            Thread cnnThread = new Thread(r);
            cnnThread.start();
            try {
                Thread.sleep(delay);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    abstract class CustomRunnable implements Runnable {
        public abstract void setDim(int dim);
    }
}

使用新参数在循环中创建新线程

3 个答案: