为什么可以'；我不能在Android Studio（JAVA）中的方法之外定义这些字段吗？

我开始学习如何在Android Studio中操作Java，但我仍然对一些看似基本的东西存在一些问题

这是我的密码：

import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    public void testClick(View view) {
        ImageView redTL = (ImageView) findViewById(R.id.redTL);
        ImageView redT = (ImageView) findViewById(R.id.redT);
        ImageView redTR = (ImageView) findViewById(R.id.redTR);
        ImageView redL = (ImageView) findViewById(R.id.redL);
        ImageView redC = (ImageView) findViewById(R.id.redC);
        ImageView redR = (ImageView) findViewById(R.id.redR);
        ImageView redBL = (ImageView) findViewById(R.id.redBL);
        ImageView redB = (ImageView) findViewById(R.id.redB);
        ImageView redBR = (ImageView) findViewById(R.id.redBR);
        ImageView yellowTL = (ImageView) findViewById(R.id.yellowTL);
        ImageView yellowT = (ImageView) findViewById(R.id.yellowT);
        ImageView yellowTR = (ImageView) findViewById(R.id.yellowTR);
        ImageView yellowL = (ImageView) findViewById(R.id.yellowL);
        ImageView yellowC = (ImageView) findViewById(R.id.yellowC);
        ImageView yellowR = (ImageView) findViewById(R.id.yellowR);
        ImageView yellowBL = (ImageView) findViewById(R.id.yellowBL);
        ImageView yellowB = (ImageView) findViewById(R.id.yellowB);
        ImageView yellowBR = (ImageView) findViewById(R.id.yellowBR);

        redTL.animate().translationYBy(1000f).setDuration(2000);
        redT.animate().translationYBy(1000f).setDuration(2000);
        redTR.animate().translationYBy(1000f).setDuration(2000);
        redL.animate().translationYBy(1000f).setDuration(2000);
        redC.animate().translationYBy(1000f).setDuration(2000);
        redR.animate().translationYBy(1000f).setDuration(2000);
        redBL.animate().translationYBy(1000f).setDuration(2000);
        redB.animate().translationYBy(1000f).setDuration(2000);
        redBR.animate().translationYBy(1000f).setDuration(2000);
        yellowTL.animate().translationYBy(1000f).setDuration(2000);
        yellowT.animate().translationYBy(1000f).setDuration(2000);
        yellowTR.animate().translationYBy(1000f).setDuration(2000);
        yellowL.animate().translationYBy(1000f).setDuration(2000);
        yellowC.animate().translationYBy(1000f).setDuration(2000);
        yellowR.animate().translationYBy(1000f).setDuration(2000);
        yellowBL.animate().translationYBy(1000f).setDuration(2000);
        yellowB.animate().translationYBy(1000f).setDuration(2000);
        yellowBR.animate().translationYBy(1000f).setDuration(2000);

    }

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

        ImageView redTL = (ImageView) findViewById(R.id.redTL);
        ImageView redT = (ImageView) findViewById(R.id.redT);
        ImageView redTR = (ImageView) findViewById(R.id.redTR);
        ImageView redL = (ImageView) findViewById(R.id.redL);
        ImageView redC = (ImageView) findViewById(R.id.redC);
        ImageView redR = (ImageView) findViewById(R.id.redR);
        ImageView redBL = (ImageView) findViewById(R.id.redBL);
        ImageView redB = (ImageView) findViewById(R.id.redB);
        ImageView redBR = (ImageView) findViewById(R.id.redBR);
        ImageView yellowTL = (ImageView) findViewById(R.id.yellowTL);
        ImageView yellowT = (ImageView) findViewById(R.id.yellowT);
        ImageView yellowTR = (ImageView) findViewById(R.id.yellowTR);
        ImageView yellowL = (ImageView) findViewById(R.id.yellowL);
        ImageView yellowC = (ImageView) findViewById(R.id.yellowC);
        ImageView yellowR = (ImageView) findViewById(R.id.yellowR);
        ImageView yellowBL = (ImageView) findViewById(R.id.yellowBL);
        ImageView yellowB = (ImageView) findViewById(R.id.yellowB);
        ImageView yellowBR = (ImageView) findViewById(R.id.yellowBR);

        redTL.setTranslationY(-1000f);
        redT.setTranslationY(-1000f);
        redTR.setTranslationY(-1000f);
        redL.setTranslationY(-1000f);
        redC.setTranslationY(-1000f);
        redR.setTranslationY(-1000f);
        redBL.setTranslationY(-1000f);
        redB.setTranslationY(-1000f);
        redBR.setTranslationY(-1000f);
        yellowTL.setTranslationY(-1000f);
        yellowT.setTranslationY(-1000f);
        yellowTR.setTranslationY(-1000f);
        yellowL.setTranslationY(-1000f);
        yellowC.setTranslationY(-1000f);
        yellowR.setTranslationY(-1000f);
        yellowBL.setTranslationY(-1000f);
        yellowB.setTranslationY(-1000f);
        yellowBR.setTranslationY(-1000f);

    }
}

这段代码运行得很好，但我想做的是在方法之外定义字段列表（ImageView），这样我就可以赢得一些行并使其更可见，而不是在方法onCreate和testClick中重复列表

然后我写了这个，但它不起作用：

import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    ImageView redTL = (ImageView) findViewById(R.id.redTL);
    ImageView redT = (ImageView) findViewById(R.id.redT);
    ImageView redTR = (ImageView) findViewById(R.id.redTR);
    ImageView redL = (ImageView) findViewById(R.id.redL);
    ImageView redC = (ImageView) findViewById(R.id.redC);
    ImageView redR = (ImageView) findViewById(R.id.redR);
    ImageView redBL = (ImageView) findViewById(R.id.redBL);
    ImageView redB = (ImageView) findViewById(R.id.redB);
    ImageView redBR = (ImageView) findViewById(R.id.redBR);
    ImageView yellowTL = (ImageView) findViewById(R.id.yellowTL);
    ImageView yellowT = (ImageView) findViewById(R.id.yellowT);
    ImageView yellowTR = (ImageView) findViewById(R.id.yellowTR);
    ImageView yellowL = (ImageView) findViewById(R.id.yellowL);
    ImageView yellowC = (ImageView) findViewById(R.id.yellowC);
    ImageView yellowR = (ImageView) findViewById(R.id.yellowR);
    ImageView yellowBL = (ImageView) findViewById(R.id.yellowBL);
    ImageView yellowB = (ImageView) findViewById(R.id.yellowB);
    ImageView yellowBR = (ImageView) findViewById(R.id.yellowBR);

    public void testClick(View view) {

        redTL.animate().translationYBy(1000f).setDuration(2000);
        redT.animate().translationYBy(1000f).setDuration(2000);
        redTR.animate().translationYBy(1000f).setDuration(2000);
        redL.animate().translationYBy(1000f).setDuration(2000);
        redC.animate().translationYBy(1000f).setDuration(2000);
        redR.animate().translationYBy(1000f).setDuration(2000);
        redBL.animate().translationYBy(1000f).setDuration(2000);
        redB.animate().translationYBy(1000f).setDuration(2000);
        redBR.animate().translationYBy(1000f).setDuration(2000);
        yellowTL.animate().translationYBy(1000f).setDuration(2000);
        yellowT.animate().translationYBy(1000f).setDuration(2000);
        yellowTR.animate().translationYBy(1000f).setDuration(2000);
        yellowL.animate().translationYBy(1000f).setDuration(2000);
        yellowC.animate().translationYBy(1000f).setDuration(2000);
        yellowR.animate().translationYBy(1000f).setDuration(2000);
        yellowBL.animate().translationYBy(1000f).setDuration(2000);
        yellowB.animate().translationYBy(1000f).setDuration(2000);
        yellowBR.animate().translationYBy(1000f).setDuration(2000);

    }

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

        redTL.setTranslationY(-1000f);
        redT.setTranslationY(-1000f);
        redTR.setTranslationY(-1000f);
        redL.setTranslationY(-1000f);
        redC.setTranslationY(-1000f);
        redR.setTranslationY(-1000f);
        redBL.setTranslationY(-1000f);
        redB.setTranslationY(-1000f);
        redBR.setTranslationY(-1000f);
        yellowTL.setTranslationY(-1000f);
        yellowT.setTranslationY(-1000f);
        yellowTR.setTranslationY(-1000f);
        yellowL.setTranslationY(-1000f);
        yellowC.setTranslationY(-1000f);
        yellowR.setTranslationY(-1000f);
        yellowBL.setTranslationY(-1000f);
        yellowB.setTranslationY(-1000f);
        yellowBR.setTranslationY(-1000f);

    }
}

有人能解释一下为什么它不起作用吗？我收到以下错误消息：

---

提前感谢您的回答

任何

findViewById（）

调用必须在

onCreate（）

中调用

setContentView（）

之后进行。当然，您可以使用例如

ImageView-redTL在任何方法之外，然后拥有
redTL=（ImageView）findViewById（R.id.redTL）在
onCreate（）
中；因此，最后，保留第一个版本更经济：/谢谢您的回答