[英]Cannot Pass the Value from Intent to another activity
編輯這是第一個活動的完整代碼:
public class login extends AppCompatActivity {
dbhelper mydb;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
mydb = new dbhelper(this);
Button btn = (Button) findViewById(R.id.Buttonregis);
btn.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
Intent i = new Intent(login.this,Reg.class);
startActivity(i);
}
});
Button lgn = (Button) findViewById(R.id.btlogin);
lgn.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
//AMBIL CONTENT EDIT_TEXT
EditText txtusername = (EditText)findViewById(R.id.ETusername);
EditText txtpassword = (EditText)findViewById(R.id.ETpassword);
//CONVERT EDIT_TEXT MENJADI STRING
String user = txtusername.getText().toString();
String pass = txtpassword.getText().toString();
//PANGGIL FUNGSI VALIDasi DARI kelas dbhelper
if(mydb.checkvalid(user,pass) == true){
Intent i = new Intent(login.this,Menu.class);
i.putExtra("nama",user);
startActivity(i);
}else{
Toast.makeText(getApplicationContext(), "Wrong ID/password", Toast.LENGTH_SHORT).show();
}
}
});
編輯這是我從第二個活動中撤出的方式:
public class Menu extends AppCompatActivity {
dbhelper mydb;
Intent intent = getIntent();
String user = intent.getExtras().getString("nama");
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_menu);
Button babout = (Button) findViewById(R.id.btabout);
babout.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
Intent about = new Intent(Menu.this,About.class);
startActivity(about);
}
});
Button bprofile = (Button) findViewById(R.id.btprofile);
bprofile.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
Intent profile = new Intent(Menu.this,Profile.class);
//profile.putExtra("bknnama",user);
startActivity(profile);
}
});
//select
Button bcheck = (Button) findViewById(R.id.btcheck);
bcheck.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
Intent check = new Intent(Menu.this,Reg.class);
startActivity(check);
}
});
Button bnovel = (Button) findViewById(R.id.btnovel);
bnovel.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
Intent about = new Intent(Menu.this,Novel_list.class);
startActivity(about);
}
});
}
}系統聲明沒有錯誤,但是當我打開應用程序並按相應的按鈕進入另一個活動時,我的應用程序被強制關閉。
當我將Intent代碼放入注釋時,該應用程序再次可以正常運行,但是我需要將用戶字符串傳遞給另一個活動。
編輯這是logcat的回復
引起原因:java.lang.NullPointerException:嘗試在空對象引用上調用虛擬方法'android.os.Bundle android.content.Intent.getExtras()'
代碼錯誤。 您必須在OnCreate方法中獲得意圖:
public class Menu extends AppCompatActivity {
dbhelper mydb;
//....
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_menu);
Intent intent = getIntent();
String user = intent.getExtras().getString("nama");
// ..rest of your code...
}
}
希望能幫助到你。 問候,CS
從這里更改您的代碼
Intent intent = getIntent();
String user = intent.getExtras().getString("nama");
至
Intent intent = getIntent();
String user = intent.getStringExtra("nama");
確保在AndroidManifest.xml中聲明了Menu.class
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