Java 为什么我的ImageView设置为全屏时会隐藏？

我只想全屏查看小尺寸的图片，所以我添加了另一个名为zoom的ImageView作为全屏视图，当我单击“上一步”时，它将隐藏。但是，我找不到错误。我已经尝试了可见性更改，但似乎没有任何问题：

public class HistoryActivity extends ActionBarActivity {

    ImageView v1 = (ImageView)findViewById(R.id.iv);
    ImageView v2 = (ImageView)findViewById(R.id.iv2);
    ImageView v3 = (ImageView)findViewById(R.id.iv3);
    ImageView v4 = (ImageView)findViewById(R.id.iv4);
    ImageView v5 = (ImageView)findViewById(R.id.iv5);
    ImageView zoom = (ImageView)findViewById(R.id.imageView5);

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_history);

        v1.setImageResource(R.drawable.pic1);
        v2.setImageResource(R.drawable.pic1);
        v3.setImageResource(R.drawable.pic1);
        v4.setImageResource(R.drawable.pic1);
        v5.setImageResource(R.drawable.pic1);
        zoom.setVisibility(View.INVISIBLE);
        v1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                zoom.setImageResource(R.drawable.pic1);
                zoom.setVisibility(View.VISIBLE);
            }
        });
        v2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                zoom.setImageResource(R.drawable.pic1);
                zoom.setVisibility(View.VISIBLE);
            }
        });
        v3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                zoom.setImageResource(R.drawable.pic1);
                zoom.setVisibility(View.VISIBLE);
            }
        });
        v4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                zoom.setImageResource(R.drawable.pic1);
                zoom.setVisibility(View.VISIBLE);
            }
        });
        v5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                zoom.setImageResource(R.drawable.pic1);
                zoom.setVisibility(View.VISIBLE);
            }
        });

        ImageButton btnBack = (ImageButton) findViewById(R.id.imageButton6);
        btnBack.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(zoom.getVisibility() != View.INVISIBLE) {
                    zoom.setVisibility(View.INVISIBLE);
                }
                else {
                    Intent myIntent = new Intent(v.getContext(), CityActivity.class);
                    startActivityForResult(myIntent, 0);
                }
            }
        });
    }
}

这样做,

ImageView v1 = (ImageView)findViewById(R.id.iv);
ImageView v2 = (ImageView)findViewById(R.id.iv2);
ImageView v3 = (ImageView)findViewById(R.id.iv3);
ImageView v4 = (ImageView)findViewById(R.id.iv4);
ImageView v5 = (ImageView)findViewById(R.id.iv5);
ImageView zoom = (ImageView)findViewById(R.id.imageView5);

在您的onCreate中，在

setContentView（）之后和之前

v1.setImageResource(R.drawable.pic1);
    v2.setImageResource(R.drawable.pic1);
    v3.setImageResource(R.drawable.pic1);
    v4.setImageResource(R.drawable.pic1);
    v5.setImageResource(R.drawable.pic1);

在调用setContentView（）之前，无法初始化视图元素。在那之前它们都是空的
 你的日志在哪里？您看到产生了哪些错误/异常了吗？Java错误/异常消息非常详细。logCat上没有错误，但如果我运行该应用程序，它将不幸停止。谢谢！它起作用了！=）我花了很多时间才解决这个问题！！你能接受这个答案吗？它也可以帮助其他人……）