Question

我是android的新手。我试图按照这些视频link中的教程进行操作。我知道这里有很多教程和相同的问题，但我想知道当我点击提交按钮时我的应用停止的确切原因。对不起，我还不熟悉他们在android studio中的功能以及系统如何工作。我尝试创建2个片段，顶部和底部片段。在顶部片段中有一个提交表单。当我单击提交按钮时。该值将显示在底部片段中。这就像将值传递给另一个片段一样。我创建了一个片段类名称TopSectionFragment

package com.example.aldrin.fragmenttutorial;

import android.content.Context;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.app.Activity;
import android.widget.Button;
import android.widget.EditText;

public class TopSectionFragment extends Fragment{
    @Nullable
    private static EditText topTextInput;
    private static EditText bottomTextInput;

    TopSectionListener activityCommander;

    public interface TopSectionListener{
        public void createMem(String top, String bottom);
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);

        Activity activity = context instanceof Activity ? (Activity) context : null;

        try{
            activityCommander = (TopSectionListener) activity;
        }catch (ClassCastException e){
            throw new ClassCastException(activity.toString());
        }
    }



    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.top_section_fragment,container,false);

        topTextInput = (EditText)view.findViewById(R.id.topText);
        bottomTextInput = (EditText)view.findViewById(R.id.bottomText);

        final Button button = (Button) view.findViewById(R.id.submitButton);

        button.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        buttonClick(v);
                    }
                }
        );

        return view;
    }

    public void buttonClick(View v){
        activityCommander.createMem(topTextInput.getText().toString(),bottomTextInput.getText().toString());
    }
}

我为底部创建了另一个片段。我把它命名为BottomPictureFragment

package com.example.aldrin.fragmenttutorial;

import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class BottomPictureFragment extends Fragment {

    private static TextView t1;
    private static TextView t2;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.bottom_picture_fragment,container,false);

        t1 = (TextView) view.findViewById(R.id.topText);
        t2 = (TextView) view.findViewById(R.id.bottomText);
        return view;
    }

    public void setMemeText(String top, String bottom){
        t1.setText(top);
        t2.setText(bottom);
    }
}

我将Kitkat用于我的项目。当我按照视频教程时， onAttach（活动活动）已被弃用。我尝试使用 onAttach（上下文上下文）但同样的问题。当我把它运行到我的华硕手机。我提交时会停止这个过程。以下是我的MainActity的代码

package com.example.aldrin.fragmenttutorial;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;


public class MainActivity extends AppCompatActivity implements TopSectionFragment.TopSectionListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public void createMem(String top, String bottom) {
        BottomPictureFragment bottomFragment = (BottomPictureFragment) getSupportFragmentManager().findFragmentById(R.id.fragment2);
        bottomFragment.setMemeText(top,bottom);
    }

}

但是如果你提供另一种解决方案来将值传递给其他片段。将不胜感激。它将帮助我学习更多。希望得到你的帮助。我只是从视频中复制代码。

我收到了这些错误

10-27 13:42:49.436 6176-6176/com.example.users.fragmenttutorial W/IInputConnectionWrapper: beginBatchEdit on inactive InputConnection
10-27 13:42:49.436 6176-6176/com.example.users.fragmenttutorial W/IInputConnectionWrapper: endBatchEdit on inactive InputConnection
10-27 13:42:51.636 6176-6176/com.example.users.fragmenttutorial D/AndroidRuntime: Shutting down VM
10-27 13:42:51.636 6176-6176/com.example.users.fragmenttutorial W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x430f2140)
10-27 13:42:51.636 6176-6176/com.example.users.fragmenttutorial E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                   Process: com.example.users.fragmenttutorial, PID: 6176
                                                                                   java.lang.NullPointerException
                                                                                       at com.example.users.fragmenttutorial.BottomPictureFragment.setMemeText(BottomPictureFragment.java:28)
                                                                                       at com.example.users.fragmenttutorial.MainActivity.createMem(MainActivity.java:18)
                                                                                       at com.example.users.fragmenttutorial.TopSectionFragment.buttonClick(TopSectionFragment.java:64)
                                                                                       at com.example.users.fragmenttutorial.TopSectionFragment$1.onClick(TopSectionFragment.java:55)
                                                                                       at android.view.View.performClick(View.java:4478)
                                                                                       at android.view.View$PerformClick.run(View.java:18698)
                                                                                       at android.os.Handler.handleCallback(Handler.java:733)
                                                                                       at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                       at android.os.Looper.loop(Looper.java:149)
                                                                                       at android.app.ActivityThread.main(ActivityThread.java:5257)
                                                                                       at java.lang.reflect.Method.invokeNative(Native Method)
                                                                                       at java.lang.reflect.Method.invoke(Method.java:515)
                                                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
                                                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
                                                                                       at dalvik.system.NativeStart.main(Native Method)

Answer 1

将数据从一个片段传递到另一个片段的简单方法如下：使用Bundle发送String/int或您要发送的任何内容：

TopSectionFragment firstFragment = new TopSectionFragment();
Bundle args = new Bundle();
args.putString("YourKey", "YourValue");
firstFragment.setArguments(args);

//Inflate the fragment
getFragmentManager().beginTransaction().add(R.id.container, firstFragment).commit();

并在BottomPictureFragment的onCreateView中：

//Retrieve the value
String value = getArguments().getString("YourKey");

您可以在这些链接中找到有关如何从一个片段与另一个片段进行通信或发送数据的更多帮助： How to pass values between Fragments

How to send data from one Fragment to another Fragment?（从这里回答）

How to pass a value from one Fragment to another in Android?

希望它有助于欢呼。

Answer 2

将值从活动或片段本身传递给片段的正确方法如下所示：

案例1：活动启动FragmentA，其值为：

getFragmentManager().beginTransaction().add(R.id.container, new FragmentA("your value")).commit();

所以在FragmentA上使用这个：

String mString;

public static FragmentA newInstance(String str) {

    Bundle bundle = new Bundle();
    bundle.putString("str", str);
    FragmentA fragment = new FragmentA();
    fragment.setArguments(bundle);
    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        mString = getArguments().getString("str");
    }
}

现在你可以在FragmentA类中使用mString变量。

案例2：FragmentA使用值调用FragmentB，您必须在FragmentA中创建一个接口并在您的活动中实现此侦听器，如：

FragmentA类创建'FragmentAListener'

public interface FragmentAListener {

    void onFragmentBClick();
}

初始化：

FragmentAListener mFragmentBLaunch;

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    mFragmentBLaunch = (FragmentAListener) context;
}

然后onclick调用它：

mFragmentBLaunch.onFragmentBClick();

之后，在Activity中实现此侦听器FragmentAListener并启动FragmentB。

祝你好运，我希望这可以帮助你。

Answer 3

从活动中，您可以将数据发送到Fragment，意图为：

Bundle bundle=new Bundle();
bundle.putString("message", "From Activity");
//set Fragmentclass Arguments
Fragmentclass fragobj=new Fragmentclass();
fragobj.setArguments(bundle);

在Fragment onCreateView方法中接收片段：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
      String strtext=getArguments().getString("message");

return inflater.inflate(R.layout.fragment, container, false);
}

如何在片段中传递值？

3 个答案: