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如何在另一个方法中使用 findViewById 变量。安卓系统

发布于 2025-01-04 12:49:38 字数 3345 浏览 3 评论 0原文

我对编程非常陌生，并且正在自学，如果我的代码很丑陋，我很抱歉。

我正在尝试创建一个类似屏幕的菜单，其中有左右箭头按钮可以更改显示的图片。我想做到这一点，以便当您在第一个图像上显示左箭头时，当显示最后一个图像时，右箭头消失。

我尝试过很多不同的方法来做到这一点，但最终总是需要一个无法解析的变量。在发布的代码中，错误位于 switch 语句中，而我尝试以其他方式对其进行编码，未解决的变量错误将位于 onClickListener 中。

你不必为我编码，只需让我知道我缺少什么概念，我会研究它。

谢谢

    package com.mystuff.mymenu;

    import android.app.Activity;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.ImageButton;
    import android.widget.ImageView;



public class PictureMenu extends Activity implements OnClickListener{

int setView = 1;    

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

    menuSet(setView);

ImageButton right = (ImageButton) findViewById(R.id.rightButton);
ImageButton left = (ImageButton) findViewById(R.id.leftButton);
right.setOnClickListener(this);
left.setOnClickListener(this);

}       
@Override
public void onClick(View v) {
if(v.getId() == R.id.rightButton){
    setView ++;
    menuSet(setView);
if(v.getId() == R.id.rightButton){
    setView ++;
        menuSet(setView);
}
    }   
    }


private void menuSet(int setView) {

    ImageView picture1 = (ImageView) findViewById(R.id.picture1);
    ImageView picture2 = (ImageView) findViewById(R.id.picture2);
    ImageView picture3 = (ImageView) findViewById(R.id.picture3);
    ImageView picture4 = (ImageView) findViewById(R.id.picture4);

    switch(setView){
    case 1: 
        left.setVisibility(View.GONE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE); //ERROR right cannot be resolved
        picture1.setVisibility(View.VISIBLE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
    case 2:
        left.setVisibility(View.VISIBLE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.VISIBLE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
    case 3: 
        left.setVisibility(View.VISIBLE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.VISIBLE);
        picture4.setVisibility(View.GONE);
        break;
    case 4: 
        left.setVisibility(View.VISIBLE); //ERROR left cannot be resolved
        right.setVisibility(View.GONE); //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.VISIBLE);
        break;
    default:
        left.setVisibility(View.GONE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.VISIBLE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
}       


}



}
原文

I am very new to programming and am teaching myself so sorry if my code is ugly.

I am trying to create a menu like screen that has left and right arrow buttons that change the picture displayed. I want to make it so when your on the first image the left arrow is gone and when on the last image is displayed the right arrow is gone.

I have tried to do this a lot of different ways but always end up needing a variable somewhere where it cannot be resolved. In the code posted the error is in the switch statement and I other ways I have tried to code it the unresolved variable error would be in the onClickListener.

You don't have to code it for me, just let me know what concept I am missing and I will study up on it.

Thanks

    package com.mystuff.mymenu;

    import android.app.Activity;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.ImageButton;
    import android.widget.ImageView;



public class PictureMenu extends Activity implements OnClickListener{

int setView = 1;    

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

    menuSet(setView);

ImageButton right = (ImageButton) findViewById(R.id.rightButton);
ImageButton left = (ImageButton) findViewById(R.id.leftButton);
right.setOnClickListener(this);
left.setOnClickListener(this);

}       
@Override
public void onClick(View v) {
if(v.getId() == R.id.rightButton){
    setView ++;
    menuSet(setView);
if(v.getId() == R.id.rightButton){
    setView ++;
        menuSet(setView);
}
    }   
    }


private void menuSet(int setView) {

    ImageView picture1 = (ImageView) findViewById(R.id.picture1);
    ImageView picture2 = (ImageView) findViewById(R.id.picture2);
    ImageView picture3 = (ImageView) findViewById(R.id.picture3);
    ImageView picture4 = (ImageView) findViewById(R.id.picture4);

    switch(setView){
    case 1: 
        left.setVisibility(View.GONE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE); //ERROR right cannot be resolved
        picture1.setVisibility(View.VISIBLE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
    case 2:
        left.setVisibility(View.VISIBLE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.VISIBLE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
    case 3: 
        left.setVisibility(View.VISIBLE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.VISIBLE);
        picture4.setVisibility(View.GONE);
        break;
    case 4: 
        left.setVisibility(View.VISIBLE); //ERROR left cannot be resolved
        right.setVisibility(View.GONE); //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.VISIBLE);
        break;
    default:
        left.setVisibility(View.GONE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.VISIBLE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
}       


}



}

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评论（2）

秋千易 2025-01-11 12:49:38

您的问题在于 right 和 left 是 onCreate() 方法的本地方法，并且无法从该方法外部看到。如果您想要它们在类范围内，请将它们设为类属性，例如：

public class PictureMenu extends Activity implements OnClickListener {

    int setView = 1; 
    ImageButton right, left;
    ...

    protected void onCreate(Bundle savedInstanceState) {
        ...
        right = (ImageButton) findViewById(R.id.rightButton);
        left = (ImageButton) findViewById(R.id.leftButton);
        ...
    }

另一个解决方案是将它们作为参数传递给 menuSet()

恕我直言，您应该首先学习正确的编程，特别是 变量范围 是。
正确格式化代码也有助于轻松发现范围。

Your problem lies in that right and left are local to onCreate() method, and cannot be seen from outside that method. If you want them class-scope, make them class attributes, e.g.:

public class PictureMenu extends Activity implements OnClickListener {

    int setView = 1; 
    ImageButton right, left;
    ...

    protected void onCreate(Bundle savedInstanceState) {
        ...
        right = (ImageButton) findViewById(R.id.rightButton);
        left = (ImageButton) findViewById(R.id.leftButton);
        ...
    }

Another solution would be passing them as arguments to menuSet()

IMHO, you should first learn proper programming, specially what variable scope is.
Also properly formatting your code helps easily spotting scopes.

回复 原文
苯莒 2025-01-11 12:49:38

这应该有效：

    package com.mystuff.mymenu;

    import android.app.Activity;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.ImageButton;
    import android.widget.ImageView;



public class PictureMenu extends Activity implements OnClickListener{

private ImageButton right, left; 

int setView = 1;    

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

    menuSet(setView);

right = (ImageButton) findViewById(R.id.rightButton);
left = (ImageButton) findViewById(R.id.leftButton);
right.setOnClickListener(this);
left.setOnClickListener(this);

}       
@Override
public void onClick(View v) {
if(v.getId() == R.id.rightButton){
    setView ++;
    menuSet(setView);
if(v.getId() == R.id.rightButton){
    setView ++;
        menuSet(setView);
}
    }   
    }


private void menuSet(int setView) {

    switch(setView){
    case 1: 
        left.setVisibility(View.GONE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE); //ERROR right cannot be resolved
        picture1.setVisibility(View.VISIBLE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
    case 2:
        left.setVisibility(View.VISIBLE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.VISIBLE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
    case 3: 
        left.setVisibility(View.VISIBLE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.VISIBLE);
        picture4.setVisibility(View.GONE);
        break;
    case 4: 
        left.setVisibility(View.VISIBLE); //ERROR left cannot be resolved
        right.setVisibility(View.GONE); //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.VISIBLE);
        break;
    default:
        left.setVisibility(View.GONE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.VISIBLE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
}       


}



}

This should work:

    package com.mystuff.mymenu;

    import android.app.Activity;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.ImageButton;
    import android.widget.ImageView;



public class PictureMenu extends Activity implements OnClickListener{

private ImageButton right, left; 

int setView = 1;    

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

    menuSet(setView);

right = (ImageButton) findViewById(R.id.rightButton);
left = (ImageButton) findViewById(R.id.leftButton);
right.setOnClickListener(this);
left.setOnClickListener(this);

}       
@Override
public void onClick(View v) {
if(v.getId() == R.id.rightButton){
    setView ++;
    menuSet(setView);
if(v.getId() == R.id.rightButton){
    setView ++;
        menuSet(setView);
}
    }   
    }


private void menuSet(int setView) {

    switch(setView){
    case 1: 
        left.setVisibility(View.GONE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE); //ERROR right cannot be resolved
        picture1.setVisibility(View.VISIBLE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
    case 2:
        left.setVisibility(View.VISIBLE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.VISIBLE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
    case 3: 
        left.setVisibility(View.VISIBLE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.VISIBLE);
        picture4.setVisibility(View.GONE);
        break;
    case 4: 
        left.setVisibility(View.VISIBLE); //ERROR left cannot be resolved
        right.setVisibility(View.GONE); //ERROR right cannot be resolved
        picture1.setVisibility(View.GONE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.VISIBLE);
        break;
    default:
        left.setVisibility(View.GONE);  //ERROR left cannot be resolved
        right.setVisibility(View.VISIBLE);  //ERROR right cannot be resolved
        picture1.setVisibility(View.VISIBLE);
        picture2.setVisibility(View.GONE);
        picture3.setVisibility(View.GONE);
        picture4.setVisibility(View.GONE);
        break;
}       


}



}
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