Android中startActivity跳转崩溃求助：传递User类型ArrayList失败

Hey there, let's break down why your app is crashing when trying to launch ScenedActivity, and fix it step by step.

Core Crash Cause: Your User Class Isn't Serializable #

The biggest issue here is that you're trying to pass an ArrayList<User> via Intent, but the User class doesn't implement a serialization interface. Android requires any object passed through Intent extras to be either Serializable or Parcelable—without this, the system throws a NotSerializableException which crashes your app immediately.

Fix: Make User Implement Serializable #

Update your User class to implement the Serializable interface (this is the simpler option for basic objects):

public class User implements Serializable {
    // Add your class fields here
    private String firstName;
    private String lastName;
    private String game;
    private int code;

    // Constructor
    public User(String firstName, String lastName, String game, int code) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.game = game;
        this.code = code;
    }

    // Optional but recommended: Add a serialVersionUID to avoid deserialization issues
    private static final long serialVersionUID = 1L;

    // Add getters/setters if needed
}

Secondary Issue: Using System Category Strings as Extra Keys #

You're using android.intent.category.LAUNCHER and android.intent.category.LAUNCHER1 as keys for your Intent extras. These are system-defined category values, and reusing them can cause conflicts or unexpected behavior. Always use custom, unique keys for your extras.

Fix: Define Custom Extra Keys #

In your MainActivity, add constants for your extra keys:

// Replace with your app's package name to ensure uniqueness
private static final String EXTRA_GREETING = "com.yourappname.extra.GREETING";
private static final String EXTRA_USER_LIST = "com.yourappname.extra.USER_LIST";

Then update your Intent code to use these keys:

Intent StartIntent = new Intent(getApplicationContext(), ScenedActivity.class);
StartIntent.putExtra(EXTRA_GREETING, "Hi");
StartIntent.putExtra(EXTRA_USER_LIST, users);
startActivity(StartIntent);

Receiving the Extras in ScenedActivity #

In ScenedActivity, retrieve the extras using the same keys:

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

    Intent incomingIntent = getIntent();
    String greeting = incomingIntent.getStringExtra(MainActivity.EXTRA_GREETING);
    ArrayList<User> receivedUsers = (ArrayList<User>) incomingIntent.getSerializableExtra(MainActivity.EXTRA_USER_LIST);

    // Use the data as needed
}

Minor Code Optimizations #

Let's clean up a few other parts of your code to avoid future issues:

• Simplify the isEmpty method: Use Android's built-in TextUtils for cleaner checks:

  private boolean isEmpty(EditText etText) {
      return TextUtils.isEmpty(etText.getText().toString().trim());
  }
  

• Avoid static variables for cod: Static variables persist in memory even after your activity is destroyed, which can lead to memory leaks or unexpected state. Use a local variable instead:

  int cod = 0;
  if (!isEmpty(Cod)) {
      cod = Integer.parseInt(Cod.getText().toString());
  }
  // No need for an else block—cod is already initialized to 0
  

Once you implement these fixes, your startActivity() call should work without crashing, and your User list will be successfully passed to ScenedActivity.

内容的提问来源于stack exchange，提问作者z games