Question

以下程序尝试计算从com.trade.seems E/AndroidRuntime: FATAL EXCEPTION: main Process: com.trade.seemys, PID: 8225 java.lang.RuntimeException: Unable to start activityComponentInfo{com.tradezap.seemysteps/com.trade.seems.ual.login.LoginActivity}: android.view.InflateException: Binary XML file line #84: Binary XML file line #84: Error inflating class android.support.design.widget.FloatingActionButton at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: android.view.InflateException: Binary XML file line #84: Binary XML file line #84: Error inflating class android.support.design.widget.FloatingActionButton at android.view.LayoutInflater.inflate(LayoutInflater.java:539) at android.view.LayoutInflater.inflate(LayoutInflater.java:423) at android.view.LayoutInflater.inflate(LayoutInflater.java:374) at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284) at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140) at com.trade.seems.ual.login.LoginActivity.onCreate(LoginActivity.java:55) at android.app.Activity.performCreate(Activity.java:6251) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: android.view.InflateException: Binary XML file line #84: Error inflating class android.support.design.widget.FloatingActionButton at android.view.LayoutInflater.createView(LayoutInflater.java:645) at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:764) at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704) at android.view.LayoutInflater.rInflate(LayoutInflater.java:835) at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798) at android.view.LayoutInflater.inflate(LayoutInflater.java:515) at android.view.LayoutInflater.inflate(LayoutInflater.java:423) at android.view.LayoutInflater.inflate(LayoutInflater.java:374) at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284) at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140) at com.trade.seems.ual.login.LoginActivity.onCreate(LoginActivity.java:55) at android.app.Activity.performCreate(Activity.java:6251) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.reflect.InvocationTargetException at java.lang.reflect.Constructor.newInstance(Native Method) at android.view.LayoutInflater.createView(LayoutInflater.java:619) at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:764) at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704) at android.view.LayoutInflater.rInflate(LayoutInflater.java:835) at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798) at android.view.LayoutInflater.inflate(LayoutInflater.java:515) at android.view.LayoutInflater.inflate(LayoutInflater.java:423) at android.view.LayoutInflater.inflate(LayoutInflater.java:374) at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284) at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140) at com.trade.seems.ual.login.LoginActivity.onCreate(LoginActivity.java:55) at android.app.Activity.performCreate(Activity.java:6251) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.NoSuchMethodError: No direct method <init>(Landroid/widget/ImageView;Landroid/support/v7/widget/AppCompatDrawableManager;)V in class Landroid/support/v7/widget/AppCompatImageHelper; or its super classes (declaration of 'android.support.v7.widget.AppCompatImageHelper' appears in /data/app/com.tradezap.seemysteps-1/base.apk) at android.support.design.widget.FloatingActionButton.<init>(FloatingActionButton.java:133) at android.support.design.widget.FloatingActionButton.<init>(FloatingActionButton.java:110) at java.lang.reflect.Constructor.newInstance(Native Method) at android.view.LayoutInflater.createView(LayoutInflater.java:619) at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:764) at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704) at android.view.LayoutInflater.rInflate(LayoutInflater.java:835) at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798) at android.view.LayoutInflater.inflate(LayoutInflater.java:515) at android.view.LayoutInflater.inflate(LayoutInflater.java:423) at android.view.LayoutInflater.inflate(LayoutInflater.java:374) at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284) at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140) at com.trade.seems.ual.login.LoginActivity.onCreate(LoginActivity.java:55) at android.app.Activity.performCreate(Activity.java:6251) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 到1的总和。我想查看中间输出，所以我添加了以下n行，但是在运行程序时它会报告分段错误，如何理解这一点？如何输出中间结果？

std::cout

Answer 1

这是你应该使用的代码：

#include <iostream>
using namespace std;

int sum_to(int value)
{   
    if(value <= 1)
        return 1;
    return sum_to(value-1) + value;
}

int main()
{
    int value = 5;
    std::cout << "sum to " << value << " is " <<  sum_to(value) << '\n';
    return 0;
}

如果你想打印中间状态，你需要多一个变量temp来存储中间结果并打印出来：

#include <iostream>
using namespace std;

int sum_to(int value)
{   
    if(value <= 1)
        return 1;
    int temp = sum_to(value-1) + value;
    std::cout << "sum to " << value << " is " <<  temp << '\n';
    return temp;
}

int main()
{
    int value = 5;
    std::cout << "sum to " << value << " is " <<  sum_to(value) << '\n';
    return 0;
}

问题在于您在{I}}所在的地方打电话sum_to，因为value始终是相同的：

int sum_to(int value)
{   
    std::cout << "sum to " << value << " is " << sum_to(value)  << '\n';
    if(value <=1)   {                            ^^^^^^^^^^^^^ this call
        return 1;
    }
    else    {
        return sum_to(value-1) + value;
    }
}

Answer 2

在检查终止条件之前，您有一个无限递归。将std::cout更改为不再调用sum_to。

Answer 3

您可以做的改进很少：

删除第一个cout，删除无休止的递归。

递归调用后添加log / cout。

int sum_to(int value)  
{  
    if(value <=1) {  
        return 1;  
    }  
    else {  
        int result = sum_to(value-1);  
        cout << "Sum to " << (value-1) << " is " << result << '\n';  
        return result + value;  
    }  
}

Answer 4

您可以将else正文替换为：

    int intermediate = sum_to(value-1) + value;
    cout << "Intermidiate: " << intermediate << endl;
    return intermediate;

为什么这种递归会产生分段错误？

4 个答案: