Android Spinner Force关闭

我尝试将Spinner添加到我的活动中，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，都会强行关闭。请帮忙。Android Spinner Force关闭

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) { 

}

}

微调代码部分

@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) { 

    } 
}

我试图摆脱所有这些处理微调代码和活动中的.xml工作正常，事件与微调等等我很确定我的.xml在这里不是问题，所以你可以只关注代码本身。

谢谢。

来源

2015-09-14 Quách Trọng Nhân

你可以展示时，应用程序崩溃输出logcat的，所以我们可以看到是什么原因造成 – o0rebelious0o

当您创建活动对象时，您正在尝试查找Spinner。在这种情况下，您将获得null。移动以下行到电话后onCreate方法setContentView

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

来源

2015-09-14 14:37:14 spgodara

Android Spinner Force关闭

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