Question

我尝试在我的活动中添加一个Spinner，到目前为止代码中没有错误，但每次我在Android模拟器上运行它时，它都会关闭。请帮助。

package com.nhan.quach.random_number_creator;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;


public class giac_mo extends ActionBarActivity implements AdapterView.OnItemSelectedListener {
    private Toolbar toolbar;
    private TextView text;
    int backButtonCount = 0;
    String[] s = {"1","2","3","4"};
    Spinner spinner = (Spinner) findViewById(R.id.spinner);
    TextView txt = (TextView) findViewById(R.id.txt);
public void onBackPressed() {
    if (backButtonCount >= 1) {
        Intent intent = new Intent(Intent.ACTION_MAIN);
        intent.addCategory(Intent.CATEGORY_HOME);
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        startActivity(intent);
    } else {
        Toast.makeText(this, "Tap Back again to exit.", Toast.LENGTH_SHORT).show();
        backButtonCount++;
    }
}

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

    toolbar = (Toolbar) findViewById(R.id.app_bar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayShowHomeEnabled(true);
    text = (TextView) findViewById(R.id.textView);
    Button button = (Button) findViewById(R.id.button);
    NavigatetionDrawerFragment drawerFragment = (NavigatetionDrawerFragment)
            getSupportFragmentManager().findFragmentById(R.id.fragment_navigation_drawer);

    drawerFragment.setup((DrawerLayout) findViewById(R.id.drawerlayout), toolbar);

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, s);
    adapter.setDropDownViewResource(android.R.layout.simple_list_item_single_choice);
    spinner.setAdapter(adapter);
    spinner.setOnItemSelectedListener(this);
    }

@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
    Toast.makeText(getApplicationContext(), ""+s[i], Toast.LENGTH_SHORT);
}

@Override
public void onNothingSelected(AdapterView<?> adapterView) {

}

}

Spinner代码部分

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

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, s);
        adapter.setDropDownViewResource(android.R.layout.simple_list_item_single_choice);
        spinner.setAdapter(adapter);
        spinner.setOnItemSelectedListener(this);
        }

    @Override
    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
        Toast.makeText(getApplicationContext(), ""+s[i], Toast.LENGTH_SHORT);
    }

    @Override
    public void onNothingSelected(AdapterView<?> adapterView) {

    }
}

我试图摆脱所有处理Spinner的代码，并且Activity在.xml中使用Spinner工作正常，所以我很确定我的.xml不是问题，所以你可以专注于代码本身。

谢谢。

Answer 1

您正在尝试在创建活动对象时找到Spinner。在这种情况下，您将获得null。调用onCreate

后，将以下行移至setContentView方法

Spinner spinner = (Spinner) findViewById(R.id.spinner);
TextView txt = (TextView) findViewById(R.id.txt);

Android Spinner Force已关闭

1 个答案: