Question

大家好，我是Android ADK的新手。我试图将方法从单独的SETUP类文件传递到主要类，即KakaMainActivity。但是，只要应用程序通过模拟器运行，它就会立即崩溃。请帮忙！

// KakaMainActivity Class

package com.example.kaka;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.Button;
import android.widget.TextView;

public class KakaMainActivity extends Activity {

    Button sendMSG1 = (Button)findViewById(R.id.button_Send1);
    Button sendMSG2 = (Button)findViewById(R.id.button_Send2);
    TextView RESULT = (TextView)findViewById(R.id.text_Result);

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

    SETUP clickAGAIN = new SETUP();
    clickAGAIN.click();
   }

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.kaka_main, menu);
    return true;
   }

}

// SETUP Class

package com.example.kaka;

import android.view.View;

public class SETUP extends KakaMainActivity {
    public void click(){
            sendMSG1.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v){
                        RESULT.setText("First message HELLO WORLD!");
            }
        });

        sendMSG2.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v){
                RESULT.setText("Second message BYE BYE");
            }
        }); 
  }
}

Answer 1

有几个问题......

首先，您不应该像这样Activity实例化

SETUP clickAGAIN = new SETUP();

如果SETUP仅用于保留您的onClick()，那么您可以拥有implements OnClickListener而不会延长任何课程。 See this answer for help with that

其次，在您使用Views或通过调用layout夸大inflater之前，您无法尝试实例化setContentView()。因此，请将KakaMainActivity更改为

Button sendMSG1; // you can declare them here
Button sendMSG2; 
TextView RESULT; 

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

    sendMSG1 = (Button)findViewById(R.id.button_Send1);  // but initialize them here
    sendMSG2 = (Button)findViewById(R.id.button_Send2);
    RESULT = (TextView)findViewById(R.id.text_Result);

此外，您应该将RESULT更改为result以符合Java标准（不是必需的，但是很好的做法）。现在它看起来像constant。

Answer 2

在setContentView

之后初始化您的观看次数

private Button sendMSG1; 
private Button sendMSG2;
private TextView RESULT;

@Override
 protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_kaka_main);
sendMSG1 = (Button)findViewById(R.id.button_Send1);
sendMSG2 = (Button)findViewById(R.id.button_Send2);
RESULT = (TextView)findViewById(R.id.text_Result);
sendMSG1.setOnClickListener(new OnClickListener() {
            @Override 
            public void onClick(View v){
                    RESULT.setText("First message HELLO WORLD!");
        }
    });
sendMSG2.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v){
            RESULT.setText("Second message BYE BYE");
        }
    });  
}

此外，您还可以在此活动中添加点击侦听器

使用匿名内部类

  sendMSG1.setOnClickListener(new OnClickListener() {
            @Override 
            public void onClick(View v){
                    RESULT.setText("First message HELLO WORLD!");
        }
    });

你也有这个

SETUP clickAGAIN = new SETUP();
clickAGAIN.click();

然后

public class SETUP extends KakaMainActivity

您实例化一个不应该执行的活动类。活动有一个ui，由startActivtiy(new Intent(param))启动。

Answer 3

您应该在设置布局后加载UI组件。

setContentView(R.layout.activity_kaka_main);
sendMSG1 = (Button)findViewById(R.id.button_Send1);
...
RESULT = (TextView)findViewById(R.id.text_Result);

Android App：无法将方法从另一个类传递到主类

3 个答案: