Android 从用户那里获取消息并显示，但当我单击按钮时，应用程序停止

我正在尝试开发一个应用程序，当按下按钮（发送）时，它会从用户那里接收消息并在新选项卡中显示消息，但当我单击按钮时，应用程序停止，而不显示消息

主要活动

 package com.example.prakash.myfirst;
 import android.content.Intent;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.View;
 import android.widget.EditText;

public class MainActivity extends AppCompatActivity {

public static final String EXTRA_MESSAGE = "com.example.Myfirst.MESSAGE";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}
public void sendMessage(View view) {
    Intent intent = new Intent(this, DisplayMessageActivity.class);
    EditText editText = (EditText) findViewById(R.id.editText);
    String message = "hi";
    intent.putExtra(EXTRA_MESSAGE, message);
    startActivity(intent);
}}

   package com.example.prakash.myfirst;

     import android.content.Intent;
     import android.support.v7.app.AppCompatActivity;
     import android.os.Bundle;
     import android.widget.TextView;

    public class DisplayMessageActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_display_message);
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

        TextView text = (TextView) findViewById(R.id.textView);
        text.setText(message);
    }
}

显示消息活动

 package com.example.prakash.myfirst;
 import android.content.Intent;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.View;
 import android.widget.EditText;

public class MainActivity extends AppCompatActivity {

public static final String EXTRA_MESSAGE = "com.example.Myfirst.MESSAGE";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}
public void sendMessage(View view) {
    Intent intent = new Intent(this, DisplayMessageActivity.class);
    EditText editText = (EditText) findViewById(R.id.editText);
    String message = "hi";
    intent.putExtra(EXTRA_MESSAGE, message);
    startActivity(intent);
}}

   package com.example.prakash.myfirst;

     import android.content.Intent;
     import android.support.v7.app.AppCompatActivity;
     import android.os.Bundle;
     import android.widget.TextView;

    public class DisplayMessageActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_display_message);
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

        TextView text = (TextView) findViewById(R.id.textView);
        text.setText(message);
    }
}

活动\u main.xml

  <Button
        android:text="@string/send_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/button"
        android:elevation="0dp"
        tools:text="@string/send_button"
        tools:hint="@string/send_button"
        android:onClick="sendMessage (MainActivity)"
        app:layout_constraintTop_toTopOf="@+id/editText"
        app:layout_constraintBottom_toBottomOf="@+id/editText"
        app:layout_constraintVertical_bias="0.6"
        android:layout_marginEnd="20dp"
        app:layout_constraintRight_toRightOf="parent" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textPersonName"
        android:ems="10"
        android:id="@+id/editText"
        android:layout_marginStart="20dp"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_marginTop="16dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_marginBottom="16dp"
        app:layout_constraintRight_toLeftOf="@+id/button"
        android:layout_marginEnd="20dp"
        android:hint="@string/edit_msg" />

    <TextView
        android:text="TextView"
        android:layout_width="196dp"
        android:layout_height="36dp"
        android:id="@+id/textView2"
        tools:layout_constraintTop_creator="1"
        tools:layout_constraintRight_creator="1"
        app:layout_constraintRight_toRightOf="parent"
        tools:layout_constraintLeft_creator="1"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_marginBottom="16dp" />
</android.support.constraint.ConstraintLayout>

---

这一行设置onClick侦听器是错误的。 android:onClick=“发送消息（main活动）”

我甚至懒得像那样宣布onClick。只需从活动中的代码设置它

Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
               sendMessage(v)
            }
          });

---

您可能也非常喜欢绑定，而不必总是使用findById并能够注释侦听器函数

post logcat Error将堆栈跟踪放在此处确保您在AndroidMainFest中添加了活动您可以发布AndroidManifest.xml吗？检查您是否在我获得的清单中添加了DisplayMessageActivity无法解析setOnClickListene（）。@prakash您拼写listener错误。。。使用IDE的自动完成功能