应用程序在android中使用多屏幕时崩溃
应用程序在android中使用多屏幕时崩溃
提问于 2021-12-19 16:48:33
我正试图在android中构建一个多屏幕应用程序，但不幸的是，它在运行过程中崩溃了。这个应用程序在主屏幕上运行得非常好，不会在MainActivity上崩溃，但当涉及到MainActivity2时，它就会崩溃。
这是我的MainActivity的Java代码：
package com.example.scrollapp;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
EditText editText;
public static final String EXTRA_NAME ="com.example.scrollapp.extra.NAME";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText=findViewById(R.id.editTextTextPersonName3);
String nametext = editText.getText().toString();
}
public void openActivity(View v){
Toast.makeText(MainActivity.this, "opening second activity", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(this,MainActivity2.class);
editText=findViewById(R.id.editTextTextPersonName3);
String nametext = editText.getText().toString();
intent.putExtra(EXTRA_NAME,nametext);
startActivity(intent);
}
}这是MainActivity2的Java：
package com.example.scrollapp;
import androidx.appcompat.app.AppCompatActivity;
import android.annotation.SuppressLint;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
public class MainActivity2 extends AppCompatActivity {
TextView textView;
@SuppressLint("SetTextI18n")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
textView.findViewById(R.id.textView);
Intent intent = getIntent();
String name = intent.getStringExtra(MainActivity.EXTRA_NAME);
textView.setText("your name is "+ name);
}
}如logcat中所示的错误：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.scrollapp, PID: 7978
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.scrollapp/com.example.scrollapp.MainActivity2}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.widget.TextView.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.widget.TextView.findViewById(int)' on a null object reference
at com.example.scrollapp.MainActivity2.onCreate(MainActivity2.java:18)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
I/Process: Sending signal. PID: 7978 SIG: 9回答 2
Stack Overflow用户
发布于 2021-12-19 17:08:19
未初始化TextView类中的MainActivity2文本视图。在textView = findViewById(R.id.textView);类中使用textView.findViewById(R.id.textView);而不是textView.findViewById(R.id.textView);。
Stack Overflow用户
发布于 2021-12-20 09:26:17
TextView的初始化不正确。初始化的正确方法是：
textView = findViewById(R.id.textView);必须在调用setcontentView方法之后实例化变量，因此必须在MainActivity2中执行以下操作
public class MainActivity2 extends AppCompatActivity {
TextView textView;
@SuppressLint("SetTextI18n")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
textView = findViewById(R.id.textView);// Change made here in this line
Intent intent = getIntent();
String name = intent.getStringExtra(MainActivity.EXTRA_NAME);
textView.setText("your name is "+ name)
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/70413448
复制相关文章
相似问题
腾讯云开发者
