java - 调用 Intent Activity 后如何修复应用程序崩溃

Question

当用户按下注册按钮并将值传递给 HomeActivity.java 时，我试图从数据库(在 LoginActivity.java 上创建)传递一个变量。在我使用 intent extras 和 bundle 之前，代码工作正常(除了传递多变的)。但是在我输入新代码后，应用程序在我按下注册按钮后立即崩溃

我尝试搜索另一个可能的重复问题，但没有一个与我的问题相同。他们中的大多数人忘记将 Activity 放在 android list 中，但我已经将 LoginActivity 放在 android list 中。当然，我注意到编译时代码没有错误

这是家庭 Activity

DatabaseHelper myDb;

Intent i = getIntent();

Bundle extras = i.getExtras();

String pname = extras.getString("P_NAME");
int pcoins = extras.getInt("P_COINS");
int pgems = extras.getInt("P_GEMS");

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Set fullscreen and no title//////////
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);

    ////////////////////////////////////

    setContentView(R.layout.main_screen);

    goProfileBtn = (Button) findViewById(R.id.profilebutton);
    shopButton = (Button) findViewById(R.id.shopbutton);
    goBarrackBtn = (Button) findViewById(R.id.barrackbutton);
    goDungeonBtn = (Button) findViewById(R.id.dungeonbutton);
    goFarmBtn = (Button) findViewById(R.id.farmbutton);
    saveBtn = (Button) findViewById(R.id.savebutton);

    NameTxt = (TextView) findViewById(R.id.playerName);
    CoinTxt = (TextView) findViewById(R.id.cointxt);
    GemTxt = (TextView) findViewById(R.id.gemtxt);

    myDb = new DatabaseHelper(this);

    ///////////////////////////////

    NameTxt.setText(pname);
    CoinTxt.setText("Coin: " + pcoins);
    GemTxt.setText("Gem: " + pgems);

    ///////// Button ///////////////////

    goProfileBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent profileSwitch = new Intent(getApplicationContext(), ProfileActivity.class);
            startActivity(profileSwitch);
        }
    });

    goFarmBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent farmSwitch = new Intent(getApplicationContext(), FarmActivity.class);
            startActivity(farmSwitch);
        }
    });

    shopButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            Intent shopSwitch = new Intent(getApplicationContext(), startGame.class);
            startActivity(shopSwitch);
        }
    });

    goBarrackBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            Intent barrackSwitch = new Intent(getApplicationContext(), startBarrack.class);
            startActivity(barrackSwitch);
        }
    });

    goDungeonBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            Intent dungeonSwitch = new Intent(getApplicationContext(), dungeonActivity.class);
            startActivity(dungeonSwitch);
        }
    });
}

@Override
public void onBackPressed() {

    final AlertDialog.Builder builder = new AlertDialog.Builder(HomeActivity.this);
    builder.setMessage("EXIT GAME");
    builder.setCancelable(true);
    builder.setNegativeButton("NOT NOW",new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
            dialogInterface.cancel();
        }
    });
    builder.setPositiveButton("YES",new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
            finish();
        }
    });

    AlertDialog alertdialog = builder.create();
    alertdialog.show();
}
    }

这是登录 Activity

EditText edit1;
EditText edit2;
EditText edit3;

Button registerBtn;
Button loginBtn;

DatabaseHelper myDb;

User player1;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //Set fullscreen and no title//////////
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);

    ///////////////////////////////////////
    setContentView(R.layout.login_screen);

    edit1 = (EditText)findViewById(R.id.editpname);
    edit2 = (EditText)findViewById(R.id.editpemail);
    edit3 = (EditText)findViewById(R.id.editppw);

    registerBtn = (Button)findViewById(R.id.registerbtn);
    loginBtn = (Button)findViewById(R.id.loginbtn);

    myDb = new DatabaseHelper(this);

    loginBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (validate()) {
                String Email = edit2.getText().toString();
                String Password = edit3.getText().toString();
                User currentUser = myDb.Authenticate(new User(null, null, Email, Password));

                if (currentUser != null) {
                    System.out.println("Successfull");

                    Intent intent = new Intent(getApplicationContext(),HomeActivity.class);
                    startActivity(intent);
                    finish();
                } else {
                    System.out.println("Unsuccessfull");
                }
            }
        }
    });

    registerBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (validate()) {
                String UserName = edit1.getText().toString();
                String Email = edit2.getText().toString();
                String Password = edit3.getText().toString();

                if (!myDb.isEmailExists(Email)) {
                    player1 = new User(null, UserName, Email, Password);
                    myDb.addUser(player1);
                    Intent i = new Intent(getApplicationContext(), HomeActivity.class);
                    Bundle extras = new Bundle();
                    extras.putString("P_NAME", player1.getName());
                    extras.putInt("P_COINS", player1.getCoins());
                    extras.putInt("P_GEMS", player1.getGems());
                    i.putExtras(extras);
                    startActivity(i);
                }
            } 
        }
    });
}

public boolean validate() {
    boolean valid = false;
    String Email = edit2.getText().toString();
    String Password = edit3.getText().toString();

    if (!android.util.Patterns.EMAIL_ADDRESS.matcher(Email).matches()) {
        valid = false;
        edit2.setError("Please enter valid email!");
    } else {
        valid = true;
        edit2.setError(null);
    }

    if (Password.isEmpty()) {
        valid = false;
        edit3.setError("Please enter valid password!");
    } else {
        if (Password.length() > 5) {
            valid = true;
            edit3.setError(null);
        } else {
            valid = false;
            edit3.setError("Password is to short!");
        }
    } 
    return valid;
}

为了可读性，我删减了一些代码

它应该将名称、硬币和 gem 以及数据库中的数据传递到 HomeActivity 中的变量中。但似乎我的代码使应用程序崩溃了

---

我还拍摄了 logcat 的快照

Answer 1

我猜你在调用 onCreate 之前向 Activity 请求 getIntent。

试试这个:

Intent i;
Bundle extras;

String pname; 
int pcoins;
int pgems; 

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    i = getIntent();
    extras = i.getExtras();

    pname = extras.getString("P_NAME");
    pcoins = extras.getInt("P_COINS");
    pgems = extras.getInt("P_GEMS");

    // follow with your onCreate code ....
}