Question

使用我正在制作的随机数发生器应用程序的Android Studio出现问题，似乎无法解析setOnClickListener。下面是应用程序的代码我似乎无法确定问题，我们将非常感谢任何帮助。

public class MainActivity extends AppCompatActivity {

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

TextView textOne = (TextView) findViewById(R.id.textView);
TextView textTwo = (TextView) findViewById(R.id.textView2);
TextView textThree = (TextView) findViewById(R.id.textView3);
TextView textFour = (TextView) findViewById(R.id.textView4);
TextView textFive = (TextView) findViewById(R.id.textView5);
TextView textSix = (TextView) findViewById(R.id.textView6);
TextView textSeven = (TextView) findViewById(R.id.textView7);
TextView textEight = (TextView) findViewById(R.id.textView8);
Button button = (Button) findViewById(R.id.button);

String[] myStamina = {"Stamina", "300%"};
String[] mySize = {"Off", "Mega", "Mini"};
String[] myHead = {"Off", "Flower", "Bunny"};
String[] myBody = {"Off", "Metal", "Clear", "Tail", "Rocket belt", "Screw", "Back shield"};
String[] myStatus = {"Off", "Curry", "Reflect"};
String[] myGravity = {"Off", "Light", "Heavy"};
String[] mySpeed = {"Off", "Fast", "Slow"};
String[] myCamera = {"Off", "Fixed", "Angled"};

int random1 = (int) ((Math.random() * 1));
int random2 = (int) ((Math.random() * 2));
int random3 = (int) ((Math.random() * 6));

button.setOnClickListener(new View.OnClickListener(){

    public void onClick(View v){
        textOne.setText(myStamina[random1]);
        textTwo.setText(mySize[random2]);
        textThree.setText(myHead[random2]);
        textFour.setText(myBody[random3]);
        textFive.setText(myStatus[random2]);
        textSix.setText(myGravity[random2]);
        textSeven.setText(mySpeed[random2]);
        textEight.setText(myCamera[random2]);
    }



});

}

Answer 1

将代码移动到onCreate()方法，如下所示：

public class MainActivity extends AppCompatActivity {

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

    TextView textOne = (TextView) findViewById(R.id.textView);
    TextView textTwo = (TextView) findViewById(R.id.textView2);
    TextView textThree = (TextView) findViewById(R.id.textView3);
    TextView textFour = (TextView) findViewById(R.id.textView4);
    TextView textFive = (TextView) findViewById(R.id.textView5);
    TextView textSix = (TextView) findViewById(R.id.textView6);
    TextView textSeven = (TextView) findViewById(R.id.textView7);
    TextView textEight = (TextView) findViewById(R.id.textView8);
    Button button = (Button) findViewById(R.id.button);

    String[] myStamina = {"Stamina", "300%"};
    String[] mySize = {"Off", "Mega", "Mini"};
    String[] myHead = {"Off", "Flower", "Bunny"};
    String[] myBody = {"Off", "Metal", "Clear", "Tail", "Rocket belt", "Screw", "Back shield"};
    String[] myStatus = {"Off", "Curry", "Reflect"};
    String[] myGravity = {"Off", "Light", "Heavy"};
    String[] mySpeed = {"Off", "Fast", "Slow"};
    String[] myCamera = {"Off", "Fixed", "Angled"};

    int random1 = (int) ((Math.random() * 1));
    int random2 = (int) ((Math.random() * 2));
    int random3 = (int) ((Math.random() * 6));

    button.setOnClickListener(new View.OnClickListener(){

        public void onClick(View v){
            textOne.setText(myStamina[random1]);
            textTwo.setText(mySize[random2]);
            textThree.setText(myHead[random2]);
            textFour.setText(myBody[random3]);
            textFive.setText(myStatus[random2]);
            textSix.setText(myGravity[random2]);
            textSeven.setText(mySpeed[random2]);
            textEight.setText(myCamera[random2]);
        }

    });


}

Answer 2

将您的TextView和Button小部件声明为global。
从onClick方法设置按钮OnCreate()。

试试这个：

public class MainActivity extends AppCompatActivity {

    TextView textOne, textTwo, textThree, textFour, textFive, textSix, textSeven, textEight;
    Button button;

    String[] myStamina = {"Stamina", "300%"};
    String[] mySize = {"Off", "Mega", "Mini"};
    String[] myHead = {"Off", "Flower", "Bunny"};
    String[] myBody = {"Off", "Metal", "Clear", "Tail", "Rocket belt", "Screw", "Back shield"};
    String[] myStatus = {"Off", "Curry", "Reflect"};
    String[] myGravity = {"Off", "Light", "Heavy"};
    String[] mySpeed = {"Off", "Fast", "Slow"};
    String[] myCamera = {"Off", "Fixed", "Angled"};

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

    textOne = (TextView) findViewById(R.id.textView);
    textTwo = (TextView) findViewById(R.id.textView2);
    textThree = (TextView) findViewById(R.id.textView3);
    textFour = (TextView) findViewById(R.id.textView4);
    textFive = (TextView) findViewById(R.id.textView5);
    textSix = (TextView) findViewById(R.id.textView6);
    textSeven = (TextView) findViewById(R.id.textView7);
    textEight = (TextView) findViewById(R.id.textView8);
    button = (Button) findViewById(R.id.button);

    int random1 = (int) ((Math.random() * 1));
    int random2 = (int) ((Math.random() * 2));
    int random3 = (int) ((Math.random() * 6));

    button.setOnClickListener(new View.OnClickListener(){

        public void onClick(View v){
            textOne.setText(myStamina[random1]);
            textTwo.setText(mySize[random2]);
            textThree.setText(myHead[random2]);
            textFour.setText(myBody[random3]);
            textFive.setText(myStatus[random2]);
            textSix.setText(myGravity[random2]);
            textSeven.setText(mySpeed[random2]);
            textEight.setText(myCamera[random2]);
        }

    });

}

Answer 3

在OnCreate（）方法中移动代码。

Answer 4

解决方案已呈现给您，现在让我们深入了解一些理论：虽然你已经将你的问题标记为与android有关，但我建议你稍微考虑一下object oriented programming principles。如果你想在你的类中拥有可执行代码（即在对象成员等上调用其他方法的代码），你应该把它放在一个方法中。这个想法是一个对象必须首先created(instantiated)才能使用它的所有字段而不用担心它的字段是否被实例化

请注意，方法外的所有代码都将执行when the class is loaded (static code blocks)或when an object of that class type is created（构造函数）。

回到原来的问题：当你尝试设置点击监听器时，android虚拟机甚至无法告诉谁是“按钮”，因为在执行的那一点，系统创建的MainActivity实例不是完全创建（实例化）。

Android studio无法解析setOnClickListener

4 个答案: