Question

在activity_main中出现的对象为null。我检查了对象和ID。我不明白我看不到的东西。

public class MainActivity extends AppCompatActivity
{

Button buttonSend;
TextView textChat;
EditText texSendMessage;
ScrollView scrollView;
Login login;
TextView textSocket;


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


    login = new Login();
    startActivity(new Intent(this, Login.class));


    buttonSend = (Button) findViewById(R.id.button_send);
    textChat = (TextView) findViewById(R.id.text_chat);
    texSendMessage = (EditText) findViewById(R.id.text_sendMessage);
    scrollView = (ScrollView) findViewById(R.id.scroll_view);
    textSocket = (TextView) findViewById(R.id.text_socket);

    OkHttpClient client = new OkHttpClient();
    String URL = "https://reqres.in/api/users?page=2";
    Request request = new Request.Builder()
            .url(URL)
            .build();
    client.newCall(request).enqueue(new Callback()
    {
        @Override
        public void onFailure(Call call, IOException e)
        {
            e.printStackTrace();
        }

        @Override
        public void onResponse(Call call, Response response) throws IOException
        {
            if (response.isSuccessful())
            {
                final String myResponse = response.body().string();

                MainActivity.this.runOnUiThread(new Runnable()
                {
                    @Override
                    public void run()
                    {
                        textSocket.setText(myResponse);
                    }
                });
            }

        }
    });


    buttonSend.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            Toast.makeText(getApplicationContext(), "Boş metin gönderilemez", Toast.LENGTH_SHORT).show();
        }
    });


    buttonSend.setOnClickListener(v -> {
        if (!searchString(texSendMessage.getText().toString()))
        {
            Toast.makeText(getApplicationContext(), "Boş metin gönderilemez", Toast.LENGTH_SHORT).show();
            texSendMessage.getText().clear();
        }

        if (texSendMessage.getText().length() == 0 || texSendMessage.getText().toString().equals(""))
        {
            Toast.makeText(getApplicationContext(), "Boş metin gönderilemez", Toast.LENGTH_SHORT).show();
        }
        else
        {
            Log.e("TAG", "texSendMessage Boyut : " + texSendMessage.getText().length());
            textChat.append(Login.getShPref().getString("USERNAME", "null") + ": " + texSendMessage.getText().toString() + '\n');
            Log.e("LOG", "texSendMessage buttonSend : /" + texSendMessage.getText().toString() + "/");
            texSendMessage.getText().clear();

            scrollView.post(new Runnable()
            {
                @Override
                public void run()
                {
                    scrollView.smoothScrollTo(0, textChat.getBottom());
                }
            });

        }
    });

}

// arama fonksiyonu ile bosluk veya yeni satırların sayısını tutup
// sadece bosluk, sadece yeni satır veya ikisinden oluşan metinlerin gönderilmesini engeller.
boolean searchString(String s)
{
    String[] strings = s.split("");
    int count = 1;
    for (int i = 0; i < s.length(); i++)
    {
        if (strings[count].equals(" ") || strings[count].equals("\n"))
        {
            count++;
        }
    }
    return count - 1 != s.length();
}

}

输出结果为：

进程：com.example.tunca.localconnect，PID：31163 java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.tunca.localconnect / com.example.tunca.localconnect.MainActivity}： java.lang.NullPointerException：尝试调用虚拟方法'void android.widget .Button.setOnClickListener（android.view.View $ OnClickListener）'对空对象的引用在上android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2858）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2933）在android.app.ActivityThread.-wrap11（未知来源：0）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1612）在android.os.Handler.dispatchMessage（Handler.java:105）在android.os.Looper.loop（Looper.java:164）在android.app.ActivityThread.main（ActivityThread.java:6710）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.Zygote $ MethodAndArgsCaller.run（Zygote.java:240）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:770）原因：java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'void android.widget.Button.setOnClickListener（android.view.View $ OnClickListener）' 在com.example.tunca.localconnect.MainActivity.onCreate（MainActivity.java:86）在android.app.Activity.performCreate（Activity.java:6980）在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1214）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2811）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2933）在android.app.ActivityThread.-wrap11（未知来源：0）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1612）在android.os.Handler.dispatchMessage（Handler.java:105）在android.os.Looper.loop（Looper.java:164）在android.app.ActivityThread.main（ActivityThread.java:6710）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.Zygote $ MethodAndArgsCaller.run（Zygote.java:240）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:770）

Answer 1

首先清除您的问题，这是一个难以理解的代码，但是我仍然可以为您提供解决问题的方法。

为什么您创建了一个在任何地方都没有使用过的Login类， login = new Login（）;
这应该在click事件上执行，您还已经在onCreate方法中调用了该intent Activity类必须添加到Manifest文件中。 startActivity（new Intent（this，Login.class））;
在点击事件中也应调用网络通话。

希望您对错误有所了解。

尝试在空对象引用上调用虚拟方法'Button.setOnClickListener（android.view.View $ OnClickListener）'

1 个答案: