如果TextView必须在onCreate中声明，我将如何编辑onCreate之外的onCreate？

Question

我遇到了一个问题，就是试图在TextView的内部调用onTap的美元，使应用程序崩溃。但是，将其移动到onCreate()可以工作，因此我无法从onTap()内部设置文本。我如何制作它，以便我可以将文本视图放在onTap中，或者使它能够访问oncreate之外的文本视图？

package com.de_veloper.idlegame;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.MenuItem;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity{


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

    //
    //
    //
    //code beginning
    //
    //
    //
    public int do_llars;
    public int upg_click_cost;
    public int upg_click_effect;
    public int upg_click_level;

    String $do_llars = String.valueOf(do_llars);
    String $upg_click_cost = String.valueOf(upg_click_cost);
    String $upg_click_level = String.valueOf(upg_click_level);
    String $upg_click_effect = String.valueOf(upg_click_effect);


    public void onTap(View view){
        if (upg_click_level == 0){
            upg_click_level = 1;
            upg_click_effect = 1;
            upg_click_effect = upg_click_level * upg_click_effect;
        }
        do_llars = do_llars + upg_click_effect;
        dollars.setText($do_llars);

    }

    public void upgradeBuy(){


    }

}

XML代码在这里：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <TextView android:text="@string/moneybutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="16pt"
        android:padding="50px"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:clickable="true"
        android:onClick="onTap"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/totaldo_llars"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:text="Total do_llars: "
        android:textSize="8pt" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/do_llars"
        android:id="@+id/dollars"
        android:layout_alignTop="@+id/totaldo_llars"
        android:layout_toRightOf="@+id/totaldo_llars"
        android:layout_toEndOf="@+id/totaldo_llars"
        android:textSize="8pt"
        android:textIsSelectable="false"
/>

</RelativeLayout>

Answer 1

问题似乎是在变数中。您正在设置字符串变量$do_llars、$upg_click_cost、$upg_click_level、$upg_click_effect，然后再将任何值赋值给do_llars、upg_click_cost、upg_click_effect、upg_click_level。因此，将您的代码修改为

public int do_llars;
public int upg_click_cost;
public int upg_click_effect;
public int upg_click_level;

String $do_llars = ""; //String.valueOf(do_llars);
String $upg_click_cost = ""; //String.valueOf(upg_click_cost);
String $upg_click_level = ""; //String.valueOf(upg_click_level);
String $upg_click_effect = ""; //String.valueOf(upg_click_effect);

public void onTap(View view){
    if (upg_click_level == 0){
        upg_click_level = 1;
        $upg_click_level = String.valueOf(upg_click_level);
        upg_click_effect = 1;
        upg_click_effect = upg_click_level * upg_click_effect;
        $upg_click_effect = String.valueOf(upg_click_effect);
    }
    do_llars = do_llars + upg_click_effect;
    $do_llars = String.valueOf(do_llars);
    dollars.setText($do_llars);
}

当您将值赋值给upg_click_cost时，您可以以同样的方式初始化$upg_click_cost。但是，与单独维护int和string变量不同，我建议您在任何地方显示do_llars, upg_click_cost, upg_click_effect, upg_click_level的值，使用String.valueOf(do_llars), String.valueOf(upg_click_cost), String.valueOf(upg_click_effect), String.valueOf(upg_click_level)，这样每次更改int变量时都不需要将更新后的值分配给String变量。

Answer 2

将dollars.setText($do_llars)改为view..setText($do_llars)；

Answer 3

本声明如下：

String $do_llars = String.valueOf(do_llars);

在为do_llars分配任何值之前执行，这可能会导致空引用异常。

解决方案:在给do_llars赋值后调用上面的语句，或者尝试Syed Zainul Abedin的答案。