Android Studio新手代码报错求助：return位置错误与方法未找到

Hey there! Let's work through those errors you're facing with your fact generator app. I'll break down each issue and show you the corrected code step by step.

First: The return outside method Error in Facts.java #

This error pops up because you tried to use a return statement inside an instance initialization block (the code wrapped in {} after your variable declarations) instead of a proper method. You also made two other critical mistakes here:

• You declared nextFact as an array (public String nextFact[];) instead of a method that returns a single String.
• Your array is named Facts (uppercase F), but you tried to return facts (lowercase f)—Java is case-sensitive, so these are treated as completely different variables.

Second: The cannot find symbol method nextFact() Error in MainActivity.java #

This is just a side effect of the first problem—your Facts class didn't actually have a nextFact() method defined. Once we fix the Facts class, this error will disappear automatically.

Corrected Code #

Facts.java #

package com.example.me.myapplication;

public class Facts {
    // Renamed to lowercase for standard Java naming conventions
    private String[] facts = {
        "This is Fact 1",
        "This is fact 2",
        "This is fact 3",
    };
    
    private int i = -1; // Start at -1 so first increment lands on index 0

    // Proper method definition for nextFact()
    public String nextFact() {
        i++;
        // Loop back to the first fact when we reach the end of the array
        if (i >= facts.length) {
            i = 0;
        }
        return facts[i];
    }
}

MainActivity.java #

Your MainActivity code is actually totally fine! The only issues were in the Facts class. Here it is again for reference:

package com.example.me.myapplication;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    TextView factBox;
    Facts factHolder = new Facts();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        factBox = (TextView) findViewById(R.id.factTextBox);
    }

    public void genFact(View view) {
        factBox.setText(factHolder.nextFact());
    }
}

Key Changes Explained #

• Renamed the array to facts (lowercase) to follow Java's variable naming rules (variables start with lowercase letters).
• Converted nextFact from an array to a proper method (public String nextFact()) that returns a single String value.
• Set i to -1 initially so the first call to nextFact() increments it to 0 (the first valid index of the array).
• Added a check to loop back to the first fact when we reach the end of the array, preventing an ArrayIndexOutOfBoundsException crash.

Once you replace your Facts.java with the corrected version, your app should compile and run without those frustrating errors. Give it a test run!

内容的提问来源于stack exchange，提问作者Kryton